The recent publication of the Full Business Case (FBC) for the A428 Black Cat to Caxton Gibbet Improvements Scheme highlights the policy inconsistencies and misleading supporting analysis that typify road investments. We have the Introduction by the Roads Minister explaining that A428 has long been seen an important section of the strategic road network that required upgrade due to its problems of congestion, poor journey time reliability and resilience, and how accordingly the Scheme will enhance journey times, support local and regional economic growth, create jobs, and improve employment and the environment.

To justify these high level objectives, the 270 page FBC grinds through all possible aspects of the case for constructing ten miles of dual carriageway. This is impressive in its way, but is the effort ‘proportionate’, to use a favourite DfT term, I wonder? Perhaps the intent is to ensure the proposal is crash-proof in the event of any further legal challenge; or perhaps to deter potential challengers from initiating such challenge. Then again, the economics of the investment look pretty marginal, based on opaque reported analysis, so perhaps extensive quantity is seen as a counterbalance to thin quality in making the case for the Scheme.

Journey time savings for all classes of vehicles, of £633m, are claimed as the main benefit, as is usual (although in 2010 prices discounted to 2010, implying some antiquity to the modelling). But this is not split between business users (cars and road freight) and non-business (commuters and others), as must have been modelled, since each class has a different value of time. In other cases I have examined, the split between business and non-business has been shown, with time savings to non-business users almost entirely offset by increased vehicle operating costs, the result of local users diverting to take advantage of faster travel provided by the improved route. The economic case for a scheme depends on the scale of such diversion, since local users pre-empt capacity intended for longer distance business users. This failure to split the journey time savings looks like intentional obfuscation.

The time saving benefits are in any case offset by quite substantial carbon disbenefits worth -£182m. My impression is these are much more than in previous road schemes, reflecting updated carbon values promulgated by the former Department of Business, Energy and Industrial Strategy. So no longer are increased carbon emissions dismissed as de minimis, at least in economic terms. Nevertheless, if, as I expect, the long run benefits of the scheme mainly take the form of enhanced access, rather than time savings, the increased vehicle-miles-travelled (known as ‘induced traffic’), would increase externalities. So carbon disbenefits are likely to have been underestimated.

Whatever the magnitude, new road capacity must generate more carbon emissions. What needs to be spelled out is the total increase in carbon from the whole road investment programme, to see to what extent this impedes delivery of transport’s contribution to Net Zero. Regrettably, the new 114 page National Networks National Policy Statement, recently published, fails to prescribe programme level estimation of carbon emissions. If neither at programme level nor at scheme level, where is this significant and unwanted damaging impact to lie?

While the cost data in the FBC are redacted, presumably to protect National Highways position in other road scheme projects out to tender, the initial benefit-cost ratio (BCR) is estimated as 0.92. To make the investment at all viable, ‘wider impacts’ of £282m have been adduced to yield an adjusted BCR of 1.63. This scale of wider impacts seems very high for a non-urban scheme, based as it is on an elaborate, yet in reality, not much more than a back-of-the-envelope calculation. It may be that it is this tenuous boost to benefits, to put the Scheme in the DfT’s medium VfM category, that has necessitated the supporting assessment and sign off by the two accounting officers, the DfT permanent secretary and National Highway’s chief executive.

For my part, I suspect that optimism bias is at work to generate even an initial BCR of 0.92, requiring yet more optimism to get to 1.63. So I would not regard the figures in the FBC as robust, even though the analysis is presented as exceptionally extensive. Yet I have some sympathy for the highways engineers at National Highways, who see this scheme as necessary to create continuous dual carriageway between the M1 at Milton Keynes and the M11 at Cambridge, with onward travel to the ports of Felixstowe and Harwich. A stretch of single carriageway in what is otherwise a dual carriageway route is, to them, offensive. Naturally they seek to add capacity to reduce congestion and achieve a free-flowing network. This approach would also seem logical and persuasive to most local politicians and business leaders not versed in the principles of transport planning and the observed road user responses to additional capacity provision, let alone the minutiae of scheme appraisal and Benefit Cost Ratio calculation.

However, congestion on roads in well-populated parts of the country typically displays morning and evening peaks, indicating use by commuters, who have choices of route. Travel patterns are not fixed and are certainly influenced by network changes. So new free-flowing routes tend to attract additional traffic, whether by diversion in the short run to achieve the saving of journey time, or in the longer run through permitting longer trips within the travel time available. Both of these are beneficial but are not the benefits conventionally modelled, nor are they allocated to the categories of traffic that underpin the original justification for the scheme. Generally, where commuters and longer distance business users share road space, free flow is difficult to achieve, particularly at peak hours.

There is a gulf between the simplistic but erroneous headline justification for this and similar road investments, and the complex, opaque and misleading quantified supporting analysis. It would be good to find a common language to bridge this gap, based on a behaviourally realistic account of what is going on, what options there are to improve matters, and what is most likely to happen in practice if changes are made. Applying the concept of Heuristics is one possible solution.

Heuristics are simple rules – rules-of-thumb – for making decisions, coming to judgement, solving problems or shaping intuitions, that work well enough in most circumstances. I want to suggest that transport planners and practitioners would benefit from relatively simple heuristics in offering advice to decision makers about addressing perceived issues of system inadequacy and the justification for providing additional capacity in a range of circumstances.

This would mean distilling the evidence from research by academics and others to yield rules-of-thumb that are intuitively credible to both practitioners and decision-makers. One problem is that research findings are often based on case studies, specific to place and time, and are path-dependent, so generalisation may be difficult. Besides, the research literature in the area of transport studies has burgeoned in recent years, not necessarily to overall professional benefit, in part the consequence of the proliferation of open access journals that charge researchers for the cost of publication, rather than rely on library subscriptions; this creates an incentive for the journal to downplay rigorous peer review and editorial oversight in the interest of increasing income, and the consequence is a proliferation of case studies that may gain academic credit but are of limited general applicability.

Moreover, the research literature may overlook the authoritative information available in official publications, including statistical series, as well as in the unofficial ‘grey literature’ publications from think-tanks and others. Hence formal reviews of the ‘research literature’ may therefore be both unwieldy and incomplete, making it hard to see the wood for the trees and so difficult to draw useful conclusions. Government departments accordingly now seem often to commission ‘rapid evidence reviews’, which give consideration to a manageable number of selected papers to save time and effort, but selection may be biased, consciously or otherwise, to support the expectations of the commissioning department, and the most important recently revealed insight and understanding may not yet be included.

In these circumstances, I believe helpful Heuristics would need to be based on a deep and wide knowledge of both publications, practice and observed data, to establish a cogent and concise framework for analysis and decisions, in accessible language, not set in stone but subject to review in the light of new evidence and experience.

One area where rules-of-thumb may be particularly useful for transport planners and decision makers is in the tackling of road traffic congestion, central to the contemporary travel experience and to transport investment, such as the A428 Scheme, but for which repeated interventions have demonstrated little impact in practice. To the extent that relief may be achieved, this is more short term than long term. Yet huge amounts of public expenditure are justified by the objective of relieving congestion and boosting connectivity, with little evidence of success at outturn.

So, let me suggest some rules-of-thumb for thinking about road traffic congestion. I will not cite chapter and verse of the evidence in support, for which see my recent book.

  • Congestion arises in or near areas of high population density where car ownership is also high. More car trips might seek to be made at times of peak demand than the road network can accommodate. Delays ensue, which motivate some road users to make other choices, including adopting alternative routes or times of departures, alternative modes of travel where available, different destinations where there are choices (such as for shopping trips), or not to travel at all (such as ordering good online). Congestion therefore is generally self-regulating in that if demand increases, delays increase and more potential trips are suppressed. Daily gridlock or long tailbacks are uncommon and arise where there are unanticipated obstructions to movement.
  • Increasing road capacity has the effect reducing delays in the short term, but thereafter attracting previously diverted and suppressed trips, as well as permitting new and longer trips, consistent with the maxim that we can’t build our way out of congestion, known from experience to be generally true. The result is additional traffic, known as ‘induced traffic’, which in the short term is the consequences of diversion of commuters and other local users on to the new capacity to save time; and, in the longer term, of road users taking advantage of faster travel to make longer trips to increase access to desired destinations, as well as changing trip origins by moving homes.
  • Interventions that reduce vehicle use initially reduce delays, but this attracts back onto the network previously suppressed trips, thus restoring congestion to what it had been. Interventions conceived as intended to reduce vehicle road use include the promotion of active travel and public transport, congestion charging and road pricing, and consolidation of freight deliveries into fewer goods vehicles.
  • Reduction in urban carriageway available to general traffic can make more space available for bus lanes, cyclists and pedestrians. This initially can increase congestion delays, which leads to drivers making alternative choices. In the longer term the intensity of congestion is difficult to reduce, but the absolute amount of congested traffic would be lessened and could be better managed to benefit the whole population.
  • Induced traffic results in more vehicle operating costs and in additional externalities, including carbon and air pollutant emissions, which public policy is seeking to reduce.
  • The orthodox economic case for road investment relies mainly on the saving of travel time. Yet the evidence is that average travel time is a long term invariant, implying that people take the benefit of faster travel in the form of improved access – to people, places, employment, services and activities, with ensuing enhanced opportunities and choices.
  • Transport models that project travel times savings, comparing the with- and without investment cases, do not reflect the reality that improved access is actually the main beneficial outcome. Access is subject to diminishing returns, implying declining returns to road investment as the road network matures.
  • The car is very popular for its utility in door-to-door travel over short to medium distances, as well as over longer distances when alternatives are less attractive, provided  congestion delays are acceptable and parking is available at both ends of the journey. These conditions may not apply in city centres, where public transport, particularly rail-based in all its forms, provides a speedy and reliable alternative to cars and buses on congested roads. But beyond city centres, in suburbs, towns and rural areas, the popularity of the car as a mode of travel against available alternatives is difficult to challenge.
  • Promotion of active travel has limited impact on car use. The evidence is that improved cycling facilities mainly attracts people from buses, which reduces farebox income and leads to reduced service levels or a requirement for more subsidy. It is difficult to be pro-active to successfully increase walking, which is the slowest mode of travel, permitting the least access to desired destinations for most people.
  • The built environment, within which are located nearly all the homes, facilities and services that are trip origins and destinations, is largely a given, with limited opportunity to increase density through brownfield or infill development. Creation of new communities on greenfield sites with choice of travel modes has proved difficult. Accordingly, there is limited scope for the creation ’15-minute cities’, an aspiration of many urban planners, aimed at reducing car use, congestion, pollution and carbon emissions.
  • As well as being popular for getting from A to B, for many people ownership of a car is attractive for a variety of lifestyle reasons. The fact that cars are generally parked for 95% of the time is a seemingly persuasive economic argument for car sharing in its various forms. But conversely, the desire to own a resource that is so little used is an indication of the value attached to ownership and convenience. This is in part why it proves difficult to shift car owners to other modes. Cars parked at the kerbside reduce carriageway available for vehicles on the move, contributing to congestion delays and deterring some road users.
  • The wide use of digital navigation (known in the roads context as satnav) has the effect of redistributing traffic. Commuters and other local users divert from existing routes to new capacity on major roads, to save time, pre-empting capacity intended for longer distance business users, including freight, so detracting from the projected economic benefits of the new capacity. In addition, traffic diverts from congested major roads to minor roads that offer a less congested alternative route, such minor roads previously used only by those with local knowledge, making them ‘rat runs’ less suited for active travel and detracting from quiet residential environments.
  • The most advanced forms of digital navigation predict journey times, so reducing uncertainty about time of arrival, which is what bothers road users most about the impact of congestion. Digital navigation is thus arguably the best means available for mitigating the perceived impact of road traffic congestion, as well as being vastly cheaper than providing new road capacity.

These rules-of-thumb about observed realities are proposed as ‘good enough’ ways of recognising and addressing the problem of congestion that we face on road networks and identifying effect means of mitigation. I suggest three questions to structure shared thinking about this and the other problems we face, amongst transport planners, politicians, other decision makes and influencers:

Q1 What’s going on here?

Q2 What options do we have to do better, that are both cost-effective and affordable?

Q3 What choices to make?

Responding to the first two questions is the task of analysts, including transport planners, economists and policy advisers, approaching problems with an open mind. Responding to the third question, with the benefits of the answers to the first two, is the task of decision makers in the public and private sectors, as well as advocates of all kinds. Better decisions would be made if those involved are clear about their roles, tasks and expectations. Heuristics, of the kind outlined above, could help them acquire good intuitions of the cost-effective options available, and give others greater insight into the basis on which decisions are made.

Nevertheless, some may argue that such heuristics serve to over-simplify what is bound to be a complex analysis of what’s going on. Albert Einstein said: ‘Make things as simple as possible, but no simpler’. Are these heuristics for understanding and reacting to congestion good enough or are they too simple? Do we still need the full panoply of the Department for Transport’s Transport Analysis Guidance to present to a small coterie of people a theoretical analysis based on problematic behavioural assumptions as to what should be done? Or, as some may believe, to justify, through virtually impossible to decipher analytical complexity (as represented by the likes of A428 business case), someone’s original hunch, then bought into tenaciously by the scheme’s promoting bodies. My own view is that narrative and dialogue based on heuristics would offer an alternative approach, well worth trying, to answer the three questions above in a generally understandable way.

This blog was the basis of an article in Local Transport Today of 21 March 2024.

The coronavirus pandemic caused major dislocation in society, not least to the amount and modes of travel, with many similarities across countries, albeit differing in detail depending on local constraints imposed on work and travel. This amounted to a ‘natural experiment’ in that an exogenous event led to large changes in travel behaviour over a two-year period, 2020-2021, before the cause faded away and normal life largely resumed, yet with some possible permanent long-term consequences. The findings of the National Travel Survey for 2022 are ambiguous as to whether we are on the path to pre-pandemic normality, or whether some permanent changes have arisen. Transport for London has recently published its annual Travel in London report for 2023 that includes relevant data for the capital. So it is worth considering the evidence for pointers to the future.

The pandemic led to two main changes in how we live and in the related demand for travel: more working from home and more shopping online.

Working from home

While some of those who do not need face-to-face contact with customers, clients or colleagues have always worked from home, the pandemic resulted in a step-change in the numbers adopting this practice. In some cases, this was a sub-optimal response to an emergency, for instance in the education sector. In other cases, this reflected advantages of not travelling to a workplace for at least part of the week, avoiding both the time and discomfort of commuting, flexibility of when to work, and perhaps benefiting from the avoidance of interruptions in the privacy of the home environment.  

For some organisations, it has been found that the workplace office could be dispensed with entirely. For many others, some form of hybrid working has emerged, with employees spending part of the week in the office, although the long-term stability of this outcome is yet to be seen. The extent of hybrid working reflects a balance between the preference of many employees for working at home and the preference of many of their managers for having people in the office – for oversight, to stimulate creative interactions and to induct new staff into the culture and practices of the organisation. This balance is affected by the state of the employment market – the demand and supply of employees with appropriate skills. The market was tight following the pandemic, with low levels of unemployment as many older workers decided not to return. But over time, this balance could shift, particularly if the benefits of agglomeration are as significant as had previously been supposed, so that businesses that have more staff on site prove to be more successful and profitable. On the other hand, businesses that commit to hybrid working may be able to attract staff from a wider area, as well as reducing the expense of maintaining office space for the full complement of staff.

Surveys by the Office for National Statistics of working adults in Britain found that while 50% reported working from home at some point in the previous seven days in the first half of 2020, early in the pandemic, this had fallen to 40% in early 2023; throughout 2022, when the restrictions of the pandemic had been lifted, the percentage of working adults reporting having worked from home varied between 25% and 40%, without a clear upward or downward trend, indicating that homeworking was resilient to the end of travel restrictions. Professionals and those in higher income bands were more likely to work from home, whereas those who require face to face contact with clients or personal engagement with facilities resumed travelling to their workplace – in education, healthcare, hospitality, retail, manufacturing and laboratories.

The emergence of a new normal involving both fully remote and hybrid working raises a question about the value of agglomeration benefits from learning, sharing, and matching in city centres. Estimation of the economic value of agglomeration has been based on econometric analysis addressing the change in productivity in relation to the change in effective economic density, with the biggest benefits accruing to knowledge-focussed businesses, despite remote or hybrid working being most feasible for such businesses. The observed movement of businesses to central locations in recent decades reflects net agglomeration benefits, the positive benefits being offset by the negative, the balance being affected by technological developments. But this may be changing.

Fleet Street, for instance, was once the physical location of the national newspapers in central London, with printing presses in the basements, print workers on floors above and editorial staff on the upper floors. This was a classic cluster, with benefits from shared facilities and staff, allowing news to travel faster and gossip to flourish. But there were offsetting disbenefits: newsprint had to be brought into central London, from where newspapers were distributed across the country overnight, and there were restrictive labour practices reflecting trade union power when the product had to be made anew each day. But then the advent of digital typesetting allowed newspapers to be printed at remote printworks with better access to transport networks, so that the editorial offices could disperse to scattered locations around London. Nowadays, ‘Fleet Steet’ is a metaphor for the newspaper industry, no longer the actual location. With hindsight, the agglomeration benefits and disbenefits were more finely balanced than had been supposed, so that new technology could tilt the balance in favour of dispersion of the cluster.

A question, then, is whether something similar may be happening more generally to knowledge-based businesses that had been benefiting from clustering in city centres. It has long been suggested that modern information and telecommunications would lead to the ‘death of distance’, yet the benefits of agglomeration seemed to trump those associated with dispersal. But then the shock of the pandemic both enforced working from home where possible and brought forward technologies to facilitate online meetings and collaboration based on broadband telecommunications that had steadily been improving. The disbenefits of agglomeration to employees in the form of the time, cost and discomfort of commuting became immediately apparent, with a consequential reluctance to return full time to the workplace. The balance of benefits and disbenefits may have shifted in favour of dispersal, although it may take time to reach a settled outcome.

For employers, increased working from home could lead to a decrease in demand for office space in the centres of cities, although this would depend on how workspace is managed to accommodate staff who are there for only part of the week. Shrinkage of space to save rental costs could make the office a less attractive destination. High quality premises with good facilities within and nearby would be preferred, to attract high quality staff. Older, lower quality buildings are becoming redundant, particularly on account of regulatory requirements to improve the energy efficiency of rented buildings. This presents opportunities to repurpose such redundant workplaces, as has long been the case by creating loft apartments from historic warehouses. The scope for repurposing more recent office accommodation can be limited by the depth of floor plan, since windows would be expected by residents of flats, and by the core location of services. Creation of laboratory space, hotels and student accommodation are being considered. Perhaps the simplest repurposing would be a reversion to residential use of inner city eighteenth and nineteenth century houses built for families with servants but subsequently converted to offices. Such repurposing would fit the concept of the 15-minute city or 20-minute neighbourhood where most needs can be met by active travel within a short distance. However, with many tenants and landlords bound by long term leases, it will take time for the extent of the full changes to occupancy to emerge

While reduced use of public transport for commuting means less crowding at peak times, it also results in less revenue for the operators and so either more subsidy is required, or the outcome is poorer service and/or higher fares. This raise the question of the role of bus and rail travel in sustaining the economic and social vibrancy of towns and cities, particularly those whose density is such the general use of the car is not viable. The scope for raising fares is limited by use made by those who cannot afford a car, which means that some external source of funding support is required. Support from government was increased substantially during the pandemic as an emergency measure, but the longer-term position remains to be seen. Transport for London (TfL) has been more dependent on operating income from passenger revenue than other major cities, hence it was hit harder by the loss of fare income during the pandemic so that tortuous negotiations with central government were required to avoid serious loss of services. The case for increased external subsidy to sustain high quality public transport fits well with the need to decarbonise the transport sector by offering alternatives to car use, given that internal combustion engine vehicles will be dominant for some years to come.

It is possible that the time saved by commuting less will be used for other travel, given the long run invariant hour a day of average travel time. If this other travel is local active travel, cycling or walking, that would be helpful for reducing the environmental impact; if by car, less so, particularly if commuting had been by public transport. Working from home also allows living more remotely from the workplace if travel to work is less frequent; this leads to changes in residential property prices as between urban and rural locations, and new construction where land with planning consent is available for development, with consequential changes for travel behaviour, particularly increased car use.

Online shopping

The other shift prompted by the pandemic was to online retail, growth of which was accentuated markedly. Yet shopping is also a social activity, and the suitability of many goods are best judged first hand, whether the feel and look of fashion items or the bulk of furnishings. Data for internet sales as a proportion of total retail sales had been on a steadily increasing trend before the pandemic, rising from around 3% in 2007 to 19% immediately before the pandemic. It spiked to reach 38% in early 2021 before falling back to 25% in mid-2022, broadly returning to trend, although for how long the upward trend will continue is as yet unclear.

The main impact of this shift to online shopping has been to reduce the attractiveness of city centre department stores, some chains of which have closed entirely while others have shut some branches and repurposed floor space in continuing locations. Stronger city centres that relied on a wide catchment area were most affected by the pandemic, while highstreets in economically weaker cities and towns were less affected, although many were already experiencing difficulty in attracting shoppers and shops on account both of general economic conditions in towns that had lost major industries and the shift to online retail. Over time, rents will adjust to a lower demand for retail floor space, either allowing new entrants or repurposing for other uses.

Implications for travel demand

Department for Transport monitoring data showed that, by April 2022, motor vehicle use nationally had returned to just over 100% of pre-pandemic levels. Public transport use grew back at slower rates and some components have tended to remain below pre-pandemic levels: by late 2023, national rail use was 85% of that observed in the same period in 2019, London Underground use a little higher, and bus use was about 90%, although there have been significant fluctuations due to school holidays, weather events, tourist flows and industrial action. Use of the Underground to central destinations bounced back more quickly at weekends than in the week.

There was a burst of recreational cycling during the first lockdown, reaching a peak of 63% above a 2013 baseline in mid-2021, falling back to a 24% increase above 2013 in late 2022, consistent with a modest rate of long-term growth. Although there were many adaptations to urban roads at the outset of the pandemic to facilitate cycling as an alternative to crowded public transport, the ultimate impact of this will not be clear until the extent of return to the office becomes evident.

The findings for 2022 as a whole, from the National Travel Survey, show only partial return to pre-pandemic levels, which may reflect the emergence of the Omicron variant in late 2021, even though travel restrictions were lifted by February 2022. Thus, average travel time prior to the pandemic was close to 60 minutes a day; during 2020 and 2021 it fell to about 45 minutes, but rose in 2022 to 53 minutes. It would not be surprising if average travel time returned to an hour a day in 2023, although it remains too early to rule out some longer term change in travel behaviour, for instance from increased working from home. Thus, the average number of commuting trips in 2022 was 85% of that in 2019, whereas the average number of education trips (including escorting) was 94% of the earlier year, indicating the greater opportunity for working from home in contrast to studying at home. Average car mileage in 2022 was 89% of that in 2019.

Data published by Transport for London provide a more granular account of the position as of late 2023 (see Figure). Overall public transport demand reached 90% of the pre-pandemic baseline. There has been a consolidation of weekday travel on Tuesdays to Thursdays, where demand is typically higher than on Mondays and Fridays (particularly on rail modes), although only 26 per cent of all London residents have the option to work from home, reflecting a ‘blue collar’ versus ‘white collar’ difference. There is also more travel on weekends than on some weekdays, and slightly longer average journey lengths, all of which appear to be becoming established features of post-pandemic demand.


A key question is whether the travel changes triggered by the pandemic will have long term impacts that will help achieve transport decarbonisation. The evidence is that car use rebounded towards pre-pandemic levels faster than public transport use, where full recovery has yet to occur, and may not do so if working from home persists as an alternative to the full week in the workplace. Active travel at best shows a slow growth trend.

The pandemic has shown that we could make major changes to lifestyle and travel behaviour under the impetus of concerns about personal health. Coming out of the pandemic, some analysts saw indications of a long-term shift to travelling less, notably those working from home making less use of the car. It is possible that working from home will prove to be a long term feature for those for whom it is practicable and where employers are amenable, resulting in more agreeable and less crowded and congested commuting. Yet this leaves open whether and how the saving in commuting time might be used, whether for nontravel activities or for other kinds of journey purpose, and by what mode.

The full impact of the pandemic on travel behaviour therefore remains to be seen, yet the emerging evidence suggests that we largely reverted to pre-pandemic travel behaviour, particularly by car, once the threat to health had receded. The impetus of the climate emergency is less immediately pressing, and so we persist in travel behaviour that meets our needs for access to people, places, activities and services, with the opportunities that ensue, hoping that advances in technology would avoid having to make hard choices about travelling less. Those seeking substantial reductions in car use to mitigate climate change can take but little comfort from the pandemic experience.

This blog was the basis for an article in Local Transport Today 23 January 2024.

The National Infrastructure Commission published its Second National Infrastructure Assessment on 18 October. The Commission’s objectives, set by the Government when it was established in 2015, are to support sustainable economic growth across all regions of the UK, improve competitiveness, improve quality of life, support climate resilience and transition to net zero carbon emissions by 2050, all within a specified long-term funding envelope for its recommendations.

The NIC’s remit is to issue a comprehensive analysis of the UK’s infrastructure requirements once every five years. This covers all economic infrastructure sectors, setting out recommendations for transport, energy, water and wastewater, flood resilience, digital connectivity and solid waste. The Assessment takes a 30-year view of the infrastructure needs within UK government competence and identifies the policies and funding to meet them.

First, I will look at some of the key conclusions and recommendations concerning transport from the NIC’s analysis, which should be fairly uncontentious, at least for transport planners and practitioners:

  • The public transport networks of England’s largest cities under-perform relative to comparable European cities. Initial priorities for investment should be in Birmingham, Bristol, Leeds and Manchester and their wider city regions, to prevent growth being constrained. The scale of capacity increases required justifies investment in rail- or tram-based projects. The government should make financial support conditional on cities committing to introduce demand management measures to reduce car journeys in city centres, and cities should provide a contribution of at least 15-25% to the funding of large projects, whether from fiscal devolution or transport user charging.
  • Transport budgets should be devolved to all local authorities responsible for strategic transport so that all places are able to maintain existing infrastructure – for example improving the condition of road surfaces – and invest for local growth. This will also help places develop locally led infrastructure strategies through which transport investment can be considered against long term goals and planned alongside housing and land use development.
  • For the national road and rail networks, the government’s first priority should be to maintain existing networks by investing adequately in maintenance and renewal, including ensuring resilience to climate change impacts.
  • In order to align the processes of road and rail capital investment, the government should set a long-term investment pipeline across road and rail around an indicative total budget envelope and with clear common strategic objectives. This should incorporate a strategic vision for the main transport corridors that includes both road and rail, ensuring that they are considered together and not separately.

The NIC goes on to say that the cancellation of HS2 beyond Birmingham, which happened only at the beginning of October, after the Assessment had been completed, leaves a major gap in the UK’s rail strategy around which a number of cities have based their economic growth plans. A new comprehensive, long term and fully costed plan is needed, says the Commission, to set out how rail improvements will address the capacity and connectivity challenges facing city regions in the North and Midlands. Who could argue with that?

More problematic, in my view, is the NIC ‘s proposition that the government should plan and invest in enhancements to the road network, targeting under-performing sections that can facilitate trade in goods, and provide better connections between cities to facilitate trade in services, observing that it is not clear that this happens at present. Accordingly, the NIC has developed a portfolio of road enhancement options, based on a connectivity metric developed by consultants, that gives each place in Britain a score to denote how well connected it is to other places, calculated by taking the average travel time between a given place and other places in Britain, and weighting them by population and distance, which are useful indicators of likely demand for travel between places. This approach is used to identify the worst performing routes on the network with substantial demand potential between key cities and towns (see map in illustration). The portfolio has been developed within a proposed budget for road investment to cover the next 20 to 30 years.

In support of its proposals for road investments, the Commission states that better connectivity will help improve trade efficiency, making it easier for businesses to move freight and trade goods and services. However, the evidence for this is problematical. For instance, one source cited by the NIC concludes that for an inter-regional transport investment, economic activity may shift either to the lower productivity region (the periphery) or to the higher productivity region (the core), the outcome depending on the underlying economic conditions and the type and scope of the investment. This is known as the Two-way Road Effect.

The emphasis of the NIC ‘s analysis is on trade in goods and services, only indirectly on non-business travel. Yet adding capacity to road and rail routes accommodates and generates more use of all kinds. On motorways, for instance, there is evidence that the increased capacity arising from converting the hard shoulder to a running lane results in local users, commuters and others, diverting to take advantage of a faster journey, pre-empting capacity intended for longer distance business users. A low connectivity metric score may well arise from delays due to morning and evening traffic congestion, indicating the existence of substantial car-based commuting. This suggests that enhancement of capacity could be expected to further increase in use by commuters, with little benefit to trade in goods and services. So, I would contend, the NIC’s approach to connectivity is too simplistic.

A further problem with the NIC’s analysis is that although it recognises that road investment will need to be compatible with plans to decarbonise transport, it concludes that the additional emissions from its proposals will not themselves substantially alter the scale of the challenge (which must therefore be borne by the plan to achieve widespread vehicle electrification by 2035). This conclusion is based on embracing the Department for Transport’s projections of road traffic demand growth of 10-28% by 2035 (as indicated in the DfT Decarbonisation Plan), while a road enhancement programme over that period would be expected to increase demand by only around 0.6 to 1.3% (based on historic evidence from a number of studies).

However, the rule of thumb, based on general experience, is that we cannot build our way out of congestion, so any increase in capacity will result in more journeys (good for trade), it will also mean more traffic, resulting in more carbon emissions – at least until fossil fuels are eliminated from road transport – and restoring congestion to what it had been (not good for trade). The Commission’s analysis, suggesting that the additional carbon emissions from its road investment proposals are relatively small, is unconvincing. What is missing is an estimate of the total additional carbon emissions from its programme of road investment, to be compared with the DfT Decarbonisation Plan projection of 620-850 MtCO2 savings from vehicle electrification between 2020 and 2050. If the total additional carbon emissions from the proposed road investments turns out to be relatively small, this implies relatively little benefits to trade; if they are large relative to the impact of vehicle electrification, then the pathway to net zero is put at risk.

A lacuna in the Commission’s analysis of transport infrastructure investment more generally is the failure to consider the application of digital technologies, both to the highway network and the vehicles using it, to enhance the performance of the system overall. The exemplar for this is the application of digital signalling on the railways that allows shorter headways between trains at peak times, thus increasing the capacity of existing track.


I had high hopes for the NIC as an alternative source of policy advice and appraisal methodology when it was set up in 2015. Its analysis of rail investments for the Midlands and North of England offered fresh thinking and was influential in shaping the Government’s plans published in 2021. But the Commission’s proposals for road investment are disappointing, both as regards methodology and conclusions. I suspect at least part of the problem is that its efforts are spread across the whole range of infrastructure investment it is required to cover, so that there is too little capability for deep thinking about how the road network functions and how additional capacity impacts on performance. The NIC needs to develop better models, methodologies and data sources if it to offer fresh thinking for road investment and challenge conventional wisdom and assumptions. If not to provide fresh thinking to that hitherto applied by the DfT, what is the purpose and benefit of the Commission?

Moreover, the Commission was badly unsighted by the Prime Minister’s announcement of the truncation of HS2. The failure of the Government to engage with it on such a major decision prompts a question about the purpose and status of the Commission. The politically-driven redistribution of the funds allocated to HS2 to local transport schemes is quite contradictory to the long term analytically-driven approach that is the remit of the NIC. So, while in principle, analysis of long term requirements for infrastructure investment must be right, in practice short term budgetary constraints and political priorities can render the long view nugatory. One has to ask whether there is a future for the NIC.

A Labour government might well be more sympathetic to the NIC’s role, given that the party in opposition in 2012 established a review of infrastructure planning under Sir John Armitt, now chair of the NIC. That review indeed proposed a National Infrastructure Commission be established. Labour has plans for major capital investment to support the transition to net zero, so having a source of independent advice on such expenditure may be continue to be attractive.

Indeed, there may be a case for merging the NIC with the Climate Change Committee, given the overlap of functions and their cross-departmental approach to future demand and supply. Yet as long as individual departments and their ministers retain responsibility for their budgets and spending plans, with the associated tendency to take a short term view, the strategic may continue to be subordinate to the politically pragmatic.

This blog post was the basis for an article in Local Transport Today of 28 November 2023

The planning system for adding significant capacity to national rail and rail networks includes a national policy statement that obviates the need for discussion of national policy at local planning enquiries. The existing statement dates from 2015, and the Department for Transport has been consulting on a updated version that takes account, in particular, of the development of policy on transport decarbonisation. The House of Commons Transport Committee has published a critical report that highlights shortcoming in the DfT draft. I submitted evidence.

The DfT draft fails to reconcile the wish to continue investment in additional road capacity with the need to achieve Net Zero objectives. We await with interest the final text of the policy statement, to see if the Department can do better, so lessening the risk successful challenges in the courts.

I previously mentioned my analysis of the widening of the M1 motorway between junctions 10 and 13. My paper has now been published in a peer-reviewed journal: Transportation Research Part A, 174, 103749. The abstract is below. Access to the article may be available free of charge for a limited period here


Cost-benefit analysis of road investments involves models that generate travel time savings as the main economic benefit. Evaluation five years after opening of a scheme to widen a section of England’s M1 motorway between junctions 10 and 13 found that the traffic moved more slowly than before the scheme opened. Comparison was made with forecast flows generated by SATURN variable demand modelling and an associated economic model. Substantial net benefits to business users were forecast, whereas for non-business users time saving benefits were more than offset by increased vehicle operation costs, consistent with diversion of local trips to take advantage of the increase in capacity. There is reason to suppose that such diversion is facilitated by the wide adoption of Digital Navigation (known generally as satnav), which makes evident the fastest route choices, even at the expense of increased fuel costs. Diversion of local trips to utilise new strategic road capacity seems likely to be a general phenomenon, which detracts from the economic case for road investment. There is therefore a good case to treat the strategic road network as mature, focussing on improving operational efficiency and exploiting vehicle-to-infrastructure connectivity in the form of Digital Navigation.

The National Infrastructure Commission has published an Advice Note, directed to the government, on roads policy, to help inform plans for the Third Road Investment Strategy (a five year investment programme for strategic interurban roads). I found this rather disappointing in its analysis of the problem.

The need to decarbonise road transport is obligatory, yet investment in new road capacity is counterproductive, whatever is achievable through the switch to electric propulsion. The Department for Transport’s draft National Networks National Policy Statement, recently issued, persists in addressing carbon emissions at scheme level, where they can continue to be treated as de minimis. There should be a requirement to estimate carbon emissions for the whole future programme (RIS3), when announced.

Given the conflict between road building and achieving decarbonisation, a critical look is needed at the econometric analysis of the relationship between interurban road investment and GDP growth, which is less than convincing. Likewise, scepticism is justified as regards projections of the growth of future traffic growth based on demographic and economic factors; per capita car use did not increase for twenty years prior to the pandemic. The main factors determining car use per capita are speed of travel, time available for travel and household car ownership, none of which seem likely to increase in the future.

The benefits of road construction are subject to diminishing returns. Arguably, the UK has a largely mature road network. For instance, cities such as Stoke-on-Trent and Wakefield, which would see themselves as lagging economically, are well located in relation to the Strategic Road Network. For devolved regional governments able to decide priorities for infrastructure investment, new road capacity may not be high, except where it is required to permit major site-specific development.

The Advice Note argues that effective prioritisation of road projects requires a focus on the links that will be most significant for trade between major regional cities. However, interurban roads are used by commuters travelling into cities. It is a common situation for traffic on interurban routes in or near populated areas to show pronounced morning and evening peaks, the consequence of commuting. If capacity is increased to alleviate congestion at these times, this will attract commuters from local roads on account of the faster travel made possible – one type of induced traffic, and one reason why we cannot build our way out of congestion. This diversion of commuters on to new major road capacity is facilitated by the wide use of Digital Navigation (generally known as satnav), which makes fastest options clear. The increased local commuting pre-empts the additional capacity intended for longer distance business users.

The proposal for a systematic analysis of the road network to see which routes are slow or unreliable is reminiscent of the approach of US highway engineers to categorising levels of service as the basis for proposals to increase capacity, thus justifying multilane freeways that attract more traffic. Yet there is a conflict between accepting the need for further road construction and demand management measures to reduce carbon emissions from the sector.

We no longer add to urban road capacity to accommodate growth of demand for road traffic; indeed, the trend is to subtract carriageway available for general traffic in favour of more space for buses, cyclists and pedestrians, plus investment in urban rail, traffic management and demand management measures. Yet the focus of interurban roads policy continues to be on investment in new capacity (although the Welsh Government has taken a different view). Given the demands of decarbonisation, a reconsideration of this traditional focus is desirable.

The prospects for autonomous vehicles as a source of economic benefit are unclear. Yet Digital Navigation is widely use and is changing travel behaviour. Road freight operators take advantage of similar digital technologies to manage their fleets effectively. There are opportunities to exploit digital technologies to improve the operational efficiency of the mature road network, which would be far more cost effective than civil engineering technologies employed to increase capacity.

The Department for Transport has scrapped plans for new smart motorways, citing current lack of confidence felt by drivers and cost pressures. It also reflects a pledge by the Prime Minister when he was campaigning last year for election as leader of the Conservative Party. However, the possibility of resuming build seems not to be ruled out since cancellation is said to ‘allow more time to track public confidence in smart motorways over a longer period’.

This cancellation is no great surprise, given the existing pause on construction until five years of safety data is available, a response of the DfT to a critical report from the House of Commons Transport Committee. There has also been a succession of reports from coroner’s inquests into deaths from fatal crashes when a broken-down vehicle on the innermost lane, previously the hard shoulder, had been impacted by a moving vehicle. It always seemed unlikely that the safety case could be made sufficiently persuasive to road users for the programme of smart motorway constriction to resume.

The attraction of so-called smart motorways was that an additional lane could be added to a motorway without further land take and without the cost and disturbance of rebuilding the bridges crossing the carriageway. The greater reliability of modern cars provided some justification. Yet the public was not convinced. The reliability of variable message signs used to close the inner lane in the event of a breakdown has been criticised. And while in the past new road construction could credibly be presented as offering safety improvement compared with historic roads, this was not evidently the case for smart motorways.

Cancellation of the current batch of proposed smart motorways raised a major question about the value for money of future road construction. This economic benefits of the forthcoming plans for the third Road Investment Strategy (RIS3) will need thorough scrutiny.

I was invited to contribute to a special issue of the journal Urban Planning on the topic ‘Car Dependence and Urban Form’. The aim of the editors was to explore the scope for developments of urban form to reduce car use. I agreed to contribute a review of the evidence of drivers’ perspectives, because I sensed there is a mismatch between the general popularity of the car and the concerns about its adverse impacts held by many transport planners and academics, such that they would wish to see a reduction in ownership and use. The paper is here. The abstract is below.

Abstract:  The concept of car dependence includes both travel to destinations for which other modes than the car are not practical and preference for car travel even when other modes are available. While the concept has been a focus for transport analysts for some time, car ownership and use have continued to grow. This reflects the utility of the car for travel on roads where drivers do not experience excessive congestion and where there is parking at both ends of the journey. Local public transport and active travel only become generally attractive alternatives to the car in dense city centres where road space for car use is limited. Reduced car dependence is facilitated by city planning that encourages increased density, opportunities for which are constrained by the stability of the built environment. As well as utility for travel to achieve access to desired destinations, car ownership is also attractive on account of positive feelings, including pride, reflecting both self-esteem and social status. The positive feelings of the population at large towards car ownership are not consistent with the critical view of many analysts, a divergence in point of view that contrasts with the general acceptance of the need to respond to climate change, for which the purchase of electric vehicles is seen as an appropriate action. Rather than advocating measures explicitly aimed at reducing car dependence, a more effective policy approach would be to increase the availability of alternative modes while mitigating the detriments of car use.

The issue of the open access journal that includes my paper is published.

Road pricing has been a perennial issue for transport policy, seen by transport economists as a rational means for allocating scarce road capacity when congestion is prevalent. The loss of revenue from road fuel duty as we switch to electric propulsion is a further reason to introduce road pricing, as the House of Commons Transport Committee argued in a report published in February 2022. The Government’s belated response, in the form of a letter from the Chancellor of the Exchequer sent in January 2023, stated that the government does not currently have plans to consider road pricing. The Transport Committee chair was not satisfied with this brush-off and has invited the Treasury to respond in greater detail to the Committee’s conclusions and recommendations.

The recent webinar, in which I participated, on the role of road pricing in achieving Net Zero, organised by Landor in partnership with SYSTRA, was therefore very timely. (View here )

Road pricing (or road user charging) has been in use for centuries in the form of toll roads, the money levied used to reimburse the cost of construction. Road pricing (or congestion charging) has been adopted in London, Stockholm and Singapore as a demand management measure. A more recent aim has been to reduce air pollution in urban areas by imposing a charge on the more polluting vehicles if they enter a Clean Air Zone (CAZ). And the need to decarbonise the transport system now prompts the question of whether and how road pricing might help achieve this objective.

Webinar contributor, David Connolly, SYSTRA, argued that to achieve a Net Zero trajectory for transport, there would need to be a significant reduction in car use. To attain this, the cost of car use would have to rise significantly, to increase the relative attractiveness of all of the alternative modes, (including car-sharing) and encourage shorter &/or less-frequent car trips. Increased costs of car ownership, of fuel and of parking were possibilities, but distance-based road pricing would have a direct impact on car use and could plug the revenue gap created by the loss of road fuel duty.

Trevor Ellis, an expert in the technology of road pricing schemes, outlined how these have been applied throughout the world. GPS-based tolling has already been adopted by a number of European counties for trucks, while many US states are trialling or operating per mile fee programmes. In Asia, Singapore and Indonesia are to implement national all-vehicle distance-based schemes soon. Trevor concluded that distance-based charging by GPS gives the flexibility to vary the charge by time and place, as well as by distance and emissions, but the biggest challenges are likely to be gaining political and public acceptance.

Silviya Barrett, of the Campaign for Better Transport, reported the outcome of a survey of public attitudes to road pricing, finding substantial agreement that the present system of vehicle taxation is in need of reform as we switch to electric vehicles (EVs), with almost half respondents supporting pay-as-you-drive as they reached the end of the survey. There would be more support if public transport were cheaper with improved connectivity.

My own view is that it would be difficult politically to use road pricing to increase the costs of motoring or of road freight, as a means to reduce vehicle usage. Our society is too dependent on road transport, so that not many politicians would be brave enough to attempt to reduce carbon emissions by a direct hike of road fuel duty or imposing an additional charge for road use. The situation of low-income motorists needing their cars for travelling to work would be a point of particular sensitivity.

However, EVs do not pay fuel duty, so there is a case that they should pay a charge for use of the roads, both to contribute to the costs of operation and maintenance of the network, and to make a contribution to the Exchequer, as do internal combustion engine (ICE) vehicles. Yet this could not be implemented immediately since the lower operating costs of EVs are important to compensate for the present higher capital costs. Nevertheless, it is expected that capital costs will decline as battery technology advances and that equivalence in capital costs of EVs and ICEs will be reached prior to the 2030 date for completion of the phasing out of sales of new ICE cars and vans.

The phasing out by 2030 is a policy that commands wide support across the political spectrum, as well as from the car manufacturers and the public, who are purchasing EVs in impressive numbers. It would be desirable to link the introduction of a road user charge for EVs to this policy approach, on the grounds of fairness as between the two kinds of vehicle in respect the operating costs incurred. This would allow time to develop a suitable road pricing system for EVs. I suggest that the existing fuel duty should remain in place for ICEs, which would avoid the anxiety that would be created, particularly amongst low-income motorists, by a major change in the charging regime. EV owners are generally better off, given the newness of the technology and the very limited second-hand market, and would be more able to cope with the cost increase.

There are variety of technologies that might be used to implement road user charging, some of which are in use other countries. Yet rather than introduce an unfamiliar technology, there would be much to be said for building on London’s experience, as the basis for a national system.

The London congestion charge has been in operation for twenty years. It has been technically successful, publicly acceptable, with no concerns about privacy despite camera surveillance for enforcement purposes, and it generates useful net revenues that support public transport provision. London has employed the same enforcement and charging system to implement the ULEZ (its version of a CAZ), initially within the central congestion charging zone, expanded last year to encompass the area within the North and South Circular Roads with fairly minimal public opposition, and intended to cover all London boroughs later this year (albeit with some local political resistance emerging in the outer boroughs). This exemplifies the scope for incremental roll-out of an established technology.

London’s daily congestion charge is based on the presence of the vehicle within the charging zone, for however long. For London’s technology to the basis for a national road user charging scheme for EVs, it would be necessary to migrate the charging arrangements to a smartphone app, since a smartphone knows where it is in time and space, so knows if it is in a charging zone at a time when the charge is levied. Smartphones are generally linked to  payment mechanisms. They would also need to be linked to the vehicle, since it is the presence of the vehicle that is chargeable, not the phone, but this should be feasible.

Adoption of the smartphone as the mechanism for payment could be incentivised by capping the daily payment at no more than the standard daily charge as paid via the existing online payment mechanism, at present £15. Once there was sufficient uptake of the app, there would be opportunity to vary the charges according to such factors as duration in the charging zone, time of day, level of congestion, location or distance within the zone. This should be publicly acceptable with the daily charge cap in place, analogous to the capping of fares on London’s buses and trains when contactless payments are made. The standard daily charge payable online would remain for those not wishing to use the app, as would the existing camera-based enforcement system.

With the app payment mechanism tested and accepted, it would be possible to extend it beyond the existing congestion charging zone. In the past, there had been a western extension of the London scheme, introduced by Ken Livingstone when he was mayor, but revoked by Boris Johnson. It would also be possible for other cities to adopt the technology, whether before or after national adoption for EVs. In the past both Manchester and Edinburgh developed plans to implement congestion charging, which, however, were rejected in referenda. Cambridge is considering a similar initiative. Adoption by a single city may seem a major step by the voters, whereas taking advantage of a national charging system in prospect may lessen their reluctance.

A national scheme of charging for road use by EVs could be introduced incrementally, whether by road type (such as motorways) or region, and by starting the charge at a low level, increasing over time as the arrangements bed down.

While a national scheme for EV road user charging might employ a separate payment app from that used in London or other cities, it would make more sense to use a single payment mechanism, apportioning the revenues between the Exchequer and the highway authorities, allowing the latter scope to vary their component of the charge to meet local needs. Over time, this could reduce the need for local authorities to bid competitively to central government pots of money for funding local transport initiatives, consistent with a general policy trend to increasing devolution of responsibilities from national to local government.

One particular possibility for the exercise of local decisions on the local component of the road user charge would be to fund improvements to public transport by increasing the charge, subject to the willingness of the electorate. More and better bus and rail services would be important in providing an alternative to car use, so facilitating decarbonisation. However, fare box revenues are insufficient to support good services, both frequency and geographical spread, so external funding is required. Yet subsidy from government, whether national or local, will always be in short supply. So revenues from road user charging seem the most likely source of further support to improve local bus and rail services.

The phasing out of sales of new ICEs by 2030 is generally agreed to be about as rapid as is feasible, but faster decarbonisation thereafter could employ the revenues from EV road user charging to fund a scrappage scheme for ICEs. This would need to be targeted at the most carbon emitting vehicles, a function of engine size and distance travelled. Age would also be important since the amount payable per vehicle would become more attractive as vehicles became older and less valuable. However, such a scrappage scheme could not usefully be implemented until there were good numbers of EVs available in the used car market.

Overall, my view is that road user charging seems unlikely to be acceptable as a means to increase the costs of road vehicle use generally in order to reduce distance travelled and carbon emissions. But there is a case for charging EVs once capital costs reduce, on grounds of fairness between vehicle with different types of propulsion. The good experience of the London congestion charge offers an incremental route to nation application, the key step being migration to a smartphone app, a familiar payment mechanism. Revenues could be apportioned between central and local government consistent with further devolution, and employed to facilitate transport decarbonisation by supporting improved public transport and funding a scrappage scheme for internal combustion engine vehicles.

So no big-bang implementation of road charging technology, rather an incremental approach that aims to carry the public along, step by step.

This blog post was the basis for an article in Local Transport Today of 20 March 2003.

The House of Commons Transport Committee is holding a timely inquiry into investment in strategic roads, following a critical report from the National Audit Office about progress with the £27 billion Road Investment Strategy 2 (RIS2) programme, now at midpoint. I submitted evidence as follows.


This submission is concerned with whether the Government’s road investment programme is meeting the needs of users, whether the programme aligns with other policies, and the relevance of technological developments. These are matters in which I have taken an interest for many years, starting when I was Chief Scientist at the Department for Transport.

Here I argue that:

  • the economic benefits of road investment have been overstated;
  • there is conflict with other Government policies, particularly Net Zero;
  • technological opportunities to improve the operational efficiency of the road network are neglected.

Economic benefits of road investment

The main economic benefit of investment in new road capacity is supposed to be the saving of travel time. The benefit-cost ratio of a proposed scheme, a measure of value for money, largely depends on the estimated value of time savings to business users and others, in relation to the cost of construction. However, there are now available evaluations of outcomes of smart motorway schemes 3-5 years after opening that find no time savings, in part on account of traffic volumes greater than forecast.

I have compared the traffic and economic forecasts with the outturns for the two smart motorway schemes for which data is available: M25 Junctions 23-27 and M1 Junctions 10-13.[i] A salient feature of the forecasts is that the value of time savings to non-business users (commuters and others) is almost entirely offset by increased vehicle operating costs. This is the result of local users diverting to the new motorway capacity to save a few minutes travel time, for instance from home to work, not fully recognising the additional fuel costs arising from the longer trip. Such diversion is facilitated by the widespread use of Digital Navigation (generally known as satnav), which makes clear the fastest routes.[ii]  Increased use by local users pre-empts capacity for longer distance business users, for whom the additional capacity was intended, and based on which the economic case for investment depends.

It is likely that these examples are representative of the general situation in that the Strategic Road Network comes under greatest stress in or near areas of population density where local and long-distance traffic compete for carriageway. Remote from such locations, for most of the time traffic generally flows freely. Investment in additional capacity that is prompted by peak hour congestion serves to accommodate more local users, who have the flexibility to choose from a number of routes.

There is a maxim that we cannot build our way out of congestion, which we know from experience to be generally true, and to which the wide use of Digital Navigation contributes. It is common for the public justification of investment in new strategic road capacity to claim the relief of congestion and boosting the economy through improved connectivity. Yet such effects are very short term, negated by the local traffic induced by the new construction that restores congestion to what it had been. Accordingly, we have been deluding ourselves about the economic benefits of road investment.

Lack of alignment with other policies

The Department for Transport recently published new National Road Traffic Projections that include a Core Scenario plus seven variant scenarios. Traffic is projected to grow in all scenarios, by between 8% and 54% by 2060, which contrasts with the widely held view that car use needs to be reduced to meet the Government’s commitment to Net Zero by 2050. Projections of traffic growth would support a future road investment programme, yet would conflict with decarbonisation policies.

The Core Scenario, based on ‘existing firm and funded policies only’, projects 22% increase in traffic to 2060 and 42% decrease in carbon emissions. Yet Net Zero by 2050 is surely a firm government commitment. The Department for Transport published its Transport Decarbonisation Plan in 2021 which claimed that this commitment could be achieved, implying that future funding and policy development would need to constrain carbon emissions from road traffic to zero by 2050. So there is an apparent inconsistency between the 2022 National Road Traffic Projections and the 2021 Transport Decarbonisation Plan.

We are at present midway through the second five-year road investment programme, known as RIS2, worth £27bn over the period 2020-2025 when announced. RIS3 is now being planned. Yet there are headwinds:

  • The potential economic benefits are likely to be overstated, as discussed above.
  • Any increase in road capacity is counterproductive for the Net Zero climate change objective since both tailpipe and embedded carbon would be increased.
  • There are public anxieties about the safety of Smart Motorways in the absence of the hard shoulder, reflected in a critical report from the House of Commons Transport Committee, to which the Government responded by halting new schemes until five years of safety data is available.
  • The Government’s Levelling Up White Paper, published in early 2022, identified a dozen ‘missions’ across departments. The single mission for the Department for Transport is aimed at improving public transport in regional cities towards that achieved in London, a sensible political and social objective. There was no reference to road investment, which is appropriate, given that congestion delays on the Strategic Road Network are less in the Midlands and North than in the South East.
  • Current pressures on public expenditure.

Given these impediments, there is a good case for treating the Strategic Road Network as mature, with the future focus on improving operational efficiency. This is the situation for urban roads, which in the past were enlarged to accommodate more traffic, but nowadays the policy direction is to reduce capacity allocated to general traffic, to encourage active travel and facilitate public transport. Similarly, the aviation sector focuses on operational efficiency – airlines maximising flying time of aircraft, use of allocated routes and passenger load factors; airports (struggling recently) optimising throughput of passengers and baggage; and air traffic management making best use of crowded airspace. The underlying discipline is operations research, not civil engineering, together with modelling and economic analysis of operations, rather than of long-lived investment.

Technological developments

A focus on operational efficiency of the Strategic Road Network would naturally prompt consideration of how best to take advantage of the huge investment in Digital Navigation that has been made, both by providers of the service and by road users. Here a very odd phenomenon is the apparent disregard of Digital Navigation by road authorities, at least as judged by their publications – no reference to satnav in those of National Highways, the Department for Transport, or local authorities (with one exception known to me, Transport for London’s collaboration with Waze). Possible explanations include: preoccupation of highways engineers with civil engineering works; the need to spend the large budget allocated to road investment; the lack of staff with professional background to cope with digital technologies; and road authorities being monopolies, so not subject to competitive pressures to maximise efficiency.

The one constituent of road users that is highly competitive is road freight, particularly that forming part of integrated logistics businesses, which makes extensive use of digital technologies to manage HGV fleets on major roads and delivery vehicles on local roads. We are conscious of this when we order goods online, with a specified delivery date and often a time slot, the ability to track packages, delivery confirmed on the doorstep, and our feedback sought on the experience – all done by algorithm. This kind of operational efficiency needs to be brought to bear on the totality of traffic on the road network.

Road network operators with such experience would naturally want to take advantage of Digital Navigation, one aim being to better cope at times of stress – major incidents, bad weather, peak holiday flows. A second aim would be to optimise use of the network in normal times, including avoiding routing traffic through unsuitable minor roads.

When road users are asked why congestion is a problem, their main concern is the uncertainty of journey time. Digital Navigation provides estimates of journey time in advance, so those who need to be at their destination at a particular time can decide when best to set out; those who are more flexible can avoid the worst of congestion; and all can choose the fastest route. Digital Navigation is vastly more cost-effective as a means to mitigate the impact of road traffic congestion than costly and ineffective civil engineering investment.

While the Department for Transport and National Highways disregard the impact of Digital Navigation on traffic flows, they do pay attention to the possible impact of autonomous vehicles. The National Road Traffic Projections includes a Technology Scenario that envisages autonomous vehicles entering the market in the 2020s and making up 50% of it by 2047. And the government intends to introduce comprehensive legislation governing driverless vehicles when parliamentary time allows.

However, any significant impact of driverless vehicles on use of the road network seems a long way off at best. Eventual benefits would be experienced by vehicle occupants whose time might be available for non-driving tasks, with little scope to increase the operational efficiency of the network. The preoccupation with this future digital technology seems perverse when an existing digital technology, Digital Navigation, is widely used and is capable of changing travel behaviour in ways that are far more cost-effective than civil engineering.

[i] Metz, D. Economic benefits of road widening: Discrepancy between outturn and forecast. Transportation Research Part A, 147, 312-319, 2021.

[ii] Metz D. The impact of digital navigation on travel behaviour. UCL Open: Environment. 2022;(4):05.