Transport

Car useTransportTravel

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.

Conclusion

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

EconomicsTransport

The Prime Minister, in his speech to the Conservative Party Conference on 4 October, announced the truncation of the iconic HS2 rail route, originally promoted as a means of levelling up the regions beyond London by halving journey time between city centres. The intention is now for high speed trains to run only between Euston and Birmingham, reverting to lower speeds on existing track to further destinations.

The economic case for HS2 was always problematic. It got worse as costs rose. The initial cost of the full Y network, comprising both the legs to Manchester and to Leeds, was put at £37 billion (2009 prices), but by the time of publication of the Full Business Case in 2020, this had risen to £109 billion (2015 prices), with further cost escalation in prospect due to inflation and real cost increases as earlier optimism bias became exposed. In July 2023 the Infrastructure and Projects Authority gave the project a red rating, meaning that successful delivery appears to be unachievable without rescoping.

So, it is not wholly surprising that Rishi Sunak pulled the plug. Yet London’s Crossrail scheme, renamed the Elizabeth Line on opening, also overran substantially both time and budget. But once opened, the design has been widely admired and performance has surpassed expectations. So, did the Prime Minister lack the courage to adhere to the strapline on his lectern when making his announcement: ‘Long term decisions for a brighter future’?

To avoid the charge of chopping HS2 to save money, the PM announced a whole raft of alternative transport projects, ranging from a metro for Leeds to more funds to fill potholes, most of which were already planned. However, a major rail investment has been replaced in part by a miscellany of road schemes, unhelpful for achieving Net Zero but consistent with the Government’s recent downplaying of urgency of this objective. And if the expenditure profile of the aggregate of these alternatives matches that of the abandoned section of HS2, then it would be many years before their benefits are realised.

The Government established the National Infrastructure Commission in 2015 to advise it on the UK’s main infrastructure needs. The Commission is shortly to publish its second National Infrastructure Assessment outlining a strategic vision over the next thirty years. The Commission has been unsighted by the HS2 announcement, which its Chair stated to be ‘deeply disappointing’.

The truncation of the largest single transport investment, planned over many years, will not reflect favourably on the UK’s ability to execute large infrastructure schemes on which a dynamic economy depends. Nor will an announcement at a party conference of a huge switch of resources from a major strategic investment to a diversity of lesser schemes seemingly designed to spread benefits thinly where these may have greatest political advantage.

There has long been an argument that better regional rail links for cities in the Midlands and the North would be offer greater economic benefits that North-South links. But any major shift of resources deserves more extensive consideration by those affected than has occurred in the present case, where the Prime Minister has wanted to make a break with his Conservative predecessors who had endorsed HS2.

EconomicsTransport

The Department for Transport has issued a draft National Networks National Policy Statement (NNNPS) for consultation . It covers major investments on the road and rail networks in England. The draft is intended to replace the version issued in 2015, before the government’s commitment to Net Zero and publication of the Transport Decarbonisation Plan. The House of Commons Transport Committee has announced an inquiry into this draft.

The DfT states that the 2015 NNNPS shall apply to projects already selected for public examination, so the new NNNPS will apply only to applications accepted after it is implemented, following the consultation. It therefore looks as though the Lower Thames Crossing tunnel, which has been accepted by the Planning Inspectorate for consideration, will be subject to the old guidance, despite construction being deferred by two years as announced in the recent Budget, which seems odd.

The purpose of such National Policy Statements is to provide guidance for decision-makers on the application of government policy when determining development consent for major infrastructure. The intention is to remove the need for consideration of fundamental national policy questions at planning inquiries. Those subject to this guidance are the scheme promoters (National Highways for most road proposals), planning inspectors, and the Secretary of State when granting Development Consent Orders.

The important question is how investment in new road capacity could be reconciled with the government’s legal commitments to achieve Net Zero greenhouse gas emissions by 2050, meeting the requirements of both the Climate Change Committee’s Sixth Carbon Budget that has been agreed by the government and the intentions of the DfT’s Transport Decarbonisation Plan. (Rail, already substantially electrified, is less of a problem.)

The draft opens by rolling the pitch, stating that the government sees a compelling need for the development of national networks (para 3.22), such that there is a presumption in favour of granting Development Consent Orders (para 4.2), while at the same time recognising the need to move away from ‘predict and provide’ (para 3.44). This is very different from the new approach of the Welsh government, which does not see a compelling need to develop its national road network.

Scheme proposals are to be supported by assessments of whole life carbon emissions, to ensure minimisation as far as possible (para 5.29). The draft states that, in reaching a decision, the ‘Secretary of State should be content that the applicant has taken all reasonable steps to reduce the total greenhouse gas emissions from a whole life carbon perspective. However, given the important role national network infrastructure plays in supporting the process of economy wide decarbonisation, the Secretary of State accepts that there are likely to be some residual emissions from construction of national network infrastructure’ (para 5.36). Moreover, a net increase in operational greenhouse gas emissions [from more traffic] is not, of itself, reason to prohibit the consenting of national network projects or to impose more restrictions on them in the planning policy framework (para 5.37). So in policy terms, additional road capacity is more important than decarbonisation.

Importantly, the application for development consent orders applies to individual schemes. There appears to be no requirement to estimate the impact on carbon emissions from an investment programme, such as the planned five-year Road Investment Strategy 3 (RIS3) due to start in 2026. Accountability scheme by scheme is not so very different from the present practice whereby National Highways argues that each individual scheme makes only a de minimus contribution to national carbon emissions, which can therefore be disregarded.

The DfT’s Transport Decarbonisation Plan made broad-brush estimates of carbon reduction from policies and programmes, for instance 1-6 MtCO2e from increased active travel over the period 2020 to 2050, and 620-850 MtCO2e for electrification of cars and vans over the same period. It is inconsistent not to recognise offsetting carbon increases from investment in new road capacity, likely to fall somewhere between the above ranges, and certainly not de minimis for the programme as a whole.

There is also a problem of modelling future carbon emissions arising from road investment. Transport models are complex and opaque, with many parameters, the value of which requires expert judgement. In consequence, the are two types of protagonist: experts who have a good working understanding of transport models because they earn their living from building and running such models; and non-experts, who are interested in the output of models but are not able to understand the assumptions, simplifications and judgements that the experts must make. Non-experts include decision makers in national and local government who have prior expectations of the economic value of particular road schemes, and whose test of a good model is that it delivers outputs, comparing with- and without-investment cases, consistent with these expectations. Other non-experts are those opposing road schemes at public inquiries, who are faced with modelled outputs as part of the promoter’s proposal that are not open to detailed scrutiny. Inspectors at planning inquiries are also non-expert in this sense.

The NNNPS requires projects to be supported by a local transport model, but planning inspectors and the Secretary of State do not need to be concerned with the national methodology and national assumptions around the key drivers of transport demand (para 4.7). In practice, most schemes on the Strategic Road Network employ local versions of a set generic traffic and economic models, typically SATURN for network traffic modelling, the outputs of which are inputs to the TUBA economic model. So, as it appears, consideration of the predictive validity of these models for projecting carbon emissions need not be considered either at a public inquiry or by the Secretary of State. One can understand why a planning inspector should not be burdened with a task for which they are not professionally trained. Nevertheless, the question is where in the decision-making process the validity of the supporting modelling might be assessed.

The need to assess the predictive validity of transport models is pointed up by the failure of standard models to project fairly short-run traffic flows in two cases of motorway widening, on the M25 and the M1, as I have recorded previously. This does not increase confidence in the ability of such models to project economic benefits and carbon emissions out to sixty years.

One particular problem of transport models is that they are largely used to justify new investment, in which context the saving of travel time is supposed to be the main economic benefit. Yet average travel time, as estimated by the National Travel Survey, has changed very little over fifty years, excepting the period of the coronavirus pandemic. The implication is that people take the benefit of faster travel as enhanced access to desired destinations, people, places, activities and services, for the opportunities and choices on offer. Travelling further, rather than using travel time savings for more productive work or agreeable leisure, means more externalities related to vehicle-miles travelled, carbon emissions in particular.

Modellers who aimed to model such access benefits, and the resulting changes in land use and value, would not be appreciated by the economists who are wedded to travel time saving as the main economic benefit of investment, nor by decision-makers who are well used to conventional economic investment appraisal. So modellers must fix their assumptions, simplifications and parameters to get outcomes that satisfy a ‘realism test’ of prior expectations, subject to conformity with unspecified standards of professional respectability.

The upshot is that the modelling of the impact of new road investments will systematically underestimate carbon emissions from the additional (induced) traffic. This makes it easier to appear to comply with the pathway to Net Zero, but means that the outcome is likely to fall short of that pathway.

Some further light is shed on this matter by the cost-benefit analysis the DfT has published in support of options to implement the Zero Emissions Vehicle Mandate, the legislative framework to fulfil the government’s objective to phase out the sale of internal combustion engine cars and vans by 2030. The need for this cost-benefit analysis is not stated, since the timing of the phase out is largely for negotiation between the government and the motor manufacturers. Perhaps the Treasury wish to be assured that this route to decarbonisation represents good value compared with other possible decarbonisation measures. Or perhaps the DfT economists wish to parade their competences after cost-benefit analysis failed to be supportive of a number of major rail and road investments.

The modelling assumes that that the switch to ZEVs could result in increased mileage per ZEV driver because electricity as fuel is cheaper than petrol or diesel (which begs the question of whether some new charge for EVs might be introduced, as I have suggested). This extra driving, a ‘rebound effect’, is supposed to lead to more congestion delays, with a very substantial cost impact: for a central sensitivity case of the preferred policy option, the abatement cost of the ZEV Mandate for cars and vans estimated as £12/tCO2e excluding the rebound effect, and £100/tCO2e including it (Tables 61 and 62).

So, the DfT thinks it would be much more costly to reduce CO2 emissions by means of the Mandate if the lower operating cost of EVs led to greater distances travelled. However, in my view, rebound of the magnitude modelled is unlikely, quite apart from the possibility of a road user charge for EVs. The per capita distance travelled by car depends on three main factors: speed of travel, time available for travel, and household car ownership. None of these are affected by the switch to electric propulsion. Vehicle operating costs have a second order impact at best, witness the growth of SUV ownership despite higher fuel use.

Paradoxically, the DfT modellers postulate additional traffic from reduced vehicle operating costs arising from electrification (mistakenly, in my view), while being in denial about the additional traffic arising from road users taking the benefit of investment in increased capacity as enhanced access involving more travel (again mistakenly).

The ZEV Mandate cost-benefit analysis states that the preferred policy option is expected to achieve emission savings of 415 MtCO2e in the period 2020-2050 (Table 29). This is substantially less than the savings from switch to electric propulsion of car and vans of 620-850 MtCO2e projected in the Transport Decarbonisation Plan, mentioned above. No clear explanation for this discrepancy is given; it may be because the present Mandate is for the period to 2030, with a further Mandate promised for 2031-35; or it may reflect the sensitivity of model outputs to input assumptions.

More generally, modelling for the ZEV Mandate exemplifies how modelling outputs can be very sensitive to input assumptions that are made in the absence of firm evidence of future travel behaviour. This is a caution that applies to most transport modelling, not least to the projections of transport sector carbon emissions to support decisions necessary to achieve reductions required by the legislative framework to achieve Net Zero.

We have been before in a situation in which there have been doubts about approaches to transport economic analysis endorsed by the DfT. Good work was done by SACTRA – the Standing Advisory Committee on Trunk Road Assessment – an independent body created by the DfT, that issued two influential reports in the 1990s. One confirmed the importance of induced traffic arising from new road construction, a view that had been resisted by the DfT since such traffic added to congested and reduced travel time savings. The other report recognised the wider economic impacts of investment, beyond the conventional time saving, vehicles operating costs and those externalities to which monetary values could be attached; estimation of such wider impacts, such as agglomeration effects, now forms part of the standard approach to investment appraisal.

Although SACTRA, by its very name, was intended to remain in existence, at least until formally stood down, it seems to have fallen into that state by not receiving new commissions. There is a need, in my view, to reconstitute it, or some similar body of independent experts, to look at the suitability of the current body of official guidance on transport economic analysis and modelling in an era when decarbonisation is a national policy priority. As it is, however, the people in DfT and their consultants, who naturally wish to please their clients, are talking to each other in an echo chamber, from which interested outsiders are excluded.

Other departments do better. The Treasury’s model of the UK economy has long been available to independent forecasters. The Energy Department collaborates with academic energy modellers and makes available the online Mackay Carbon Calculator that allows users to explore the options for reducing carbon emissions. Modelling of the coronavirus pandemic was largely carried out collaboratively by academic groups whose models and outputs were public for all to debate. And the modelling of climate change is carried out openly, collaboratively and internationally as input to the reports of the Intergovernmental Panel on Climate Change.

Th DfT instigated a move to update the National Transport Model to generate a new version, NTMV5, intended to be open to other users, but this seems not to have worked out in that the National Road Traffic Projections 2022 employed the previous version (as I have noted). The DfT should explain what went wrong, and should engage openly with those beyond the Department and its immediate advisers on how best to model the decarbonisation of the transport sector.

This blog post is the basis for an article in Local Transport Today 23 May 2023.

My written evidence to the House of Commons Transport Committee inquiry into the National Networks National Policy Statement is based on this blog.

TransportTravel

The Department for Transport has recently issued a new set of National Road Traffic Projections (known as ‘forecasts’ in the past, ‘projections’ perhaps indicating rather less commitment to the findings). These apply to England and Wales and look ahead as far as 2060. The new projections are derived from the DfT’s National Transport Model (NTM), which has been developed and updated since the 2018 forecasts –  so it is claimed, but see below.

The projections relate to a set of Common Analytical Scenarios, developed by DfT with the aims of better assessing uncertainty in scheme appraisal. There is a Core Scenario plus seven variants illustrating differences in economic growth, regional distribution of population, behavioural change, new technology and decarbonisation. Except for the Behavioural Change scenario, the other variants were created by changing some of the Core Scenario assumptions. For the Core Scenario, relationships between the key drivers of demand and road traffic are broadly assumed to continue in line with historical trends.

A noteworthy feature of the new projections is that traffic is expected to grow in all scenarios, by between 8% and 54% to 2060. This contrasts with the widely held view that car use needs to be reduced to meet the Government’s commitment to Net Zero by 2050, although this is not the DfT’s view. Projections of CO2 reductions to 2060 range from 38% to 98%, depending on scenario.

The Core Scenario is based on ‘existing firm and funded policies only’ and projects a 22% increase in traffic to 2060 and a 42% decrease in carbon emissions. Yet Net Zero by 2050 is surely a firm government commitment. The DfT published its Transport Decarbonisation Plan in 2021 which projected that this would be achievable, implying that future funding and policy development would need to constrain carbon emissions from road traffic to that indicated by the low carbon scenario projections. In which case, one might wonder why publish high carbon projections that go less than half way to achieving Net Zero.

This notion of ‘existing firm and funded policies only’ is stated as encompassing published plans or funded policies. So perhaps the civil servants are drawing attention to the shortcomings of the Transport Decarbonisation Plan, which was pretty vague about the details, particularly about the achievement of behavioural change. Carbon emissions under the Core Scenario are projected to fall initially quite rapidly, but then level off, apparently because ‘the details of future car and LGV regulations to reduce CO2e emissions beyond this point have yet to be finalised.’ (para 4.15 of the NRTP). Certainly, the details of the ‘ZEV Mandate’ remain to be settled – this is intended to oblige manufacturers to sell a specified increasing proportion of zero emission vehicles during the transition – a relevant factor may be the availability of battery production in the UK, which may require government financial support. Perhaps ministers are having a wobble about this Mandate, leading the civil servants to point up the implications for Net Zero of a weakening of policy intent. Nevertheless, it all seems very odd. If no new cars and vans propelled solely internal combustion engines are to be sold after 2030 (hybrids after 2035), then the normal turnover of vehicles would mean continuing decarbonisation until all internal combustion engine vehicles are scrapped (the average age of car at scrappage is around 14 years).

Congestion delays are projected to increase by between 4% and 59% by 2060, depending on scenario, which would provide a justification for creating more capacity. So another possible explanation of the ‘firm and funded’ qualifier is that no account has been taken of a future road investment programme, in particular RIS3 for the period 2025-2030, currently being planned.

In contrast to the Core Scenario, there are three scenarios that project carbon emissions reducing to near zero by 2050. The Vehicle-led and Mode-balanced Decarbonisation Scenarios assume high and fast uptake of EVs and other zero emission vehicles ‘in line with the government’s stated ambitions to end the sale of diesel and petrol cars, vans, HGVs,
and buses/coaches.’ (para 4.48). The Technology Scenario adds a high uptake of connected and autonomous vehicles.

A further scenario of interest is a Behavioural Change Scenario, involving new ways of working, shopping and travelling. This reflects past falling trends in driving licence holding by young people and in trip rates for most purposes, as well as coronavirus pandemic-induced changes in behaviour that are assumed to continue. Some of the latter assumptions are quite striking: 40% reduction in education trips by 2041, 39% in commuting, 41% in personal business, and 55% reduction in visiting friends and relatives (para 3.37). While it is welcome that the DfT is addressing the scope for changes in travel behaviour, these particular assumptions seem on the high side. Nevertheless, the impact of these behaviour changes is surprisingly small – only to level off the growth of car traffic, with van traffic increasing by 45% to 2060 (para 4.39), to compensate for car trips not taken. Car carbon emissions are similar to those of the Core Scenario, indicating that behavioural change in itself is expected to make minimal impact.

The new traffic projections adhere to the traditional practice of predicting demand for road travel driven predominantly by changes in travel costs, population and economic growth, 90% of demand growth being attributed to these factors. A large number of other factors are considered, which is appropriate since they are relevant. The outcome is an extremely detailed formulation of a set of scenarios, which therefore avoids criticism that potentially important factors have been disregarded, but it is then hard to see the wood for the trees.

Big picture

So, let’s stand back from the detail, to see the big picture, which in my view is this: the National Travel Survey has found a gradual decline in per capita travel since the turn of the century, including decline in the average number of trips taken and in distance travelled by car (prior to the pandemic) (see Chart above). This followed rapid growth in car use in the last century, mainly the result of increasing car ownership. But household car ownership has stabilised, with some three-quarters of households owning one or more cars or vans. There was a clear break in trend at the turn of the century, which implies a change in relationships between the determinants of demand and growth of car use. Accordingly, for modelling purposes, such relationships (known as elasticities) need to be forward-looking; assuming continuity of historic trends, as does the Core Scenario, is inappropriate.

The average distance travelled per capita by car depends mainly on three factors: speed of travel, time available for travel, and level of car ownership. The first two seem unlikely to change in the future, and while there has been growth of the number of cars owned within car-owning households, the second or third car tends to be used less than the first. The impact of economic growth and income growth on per capita car use is a second order effect, seen mainly as the purchase of larger, more expensive and fuel-consuming vehicles, notably SUVs. The unvarying travel time constraint, of about an hour a day on average, limits the distance that can be travelled, irrespective of income. The DfT Projections assume that three-quarters of the projected traffic growth is driven by increases in GDP and reduced costs of driving (para 4.7), which seems improbable.

That leaves population growth, which the new traffic projections take from the Office of Budget Responsibility as an overall 4% increase by 2060, and which therefore would have a very small impact on travel demand. The consequences for road traffic growth would depend on the extent to which the additional inhabitants were accommodated in new homes on greenfield sites where car use would be the norm; or at higher density within existing urban areas, where public transport would be relevant. Unfortunately if understandably, the Regional Scenario considers accommodating the population growth in regions beyond the Wider South East, which may be relevant to the Levelling Up agenda but has little impact on overall traffic or carbon emissions.

So, I would not expect much future change in either per capita car use or total road traffic, based on recent trends. This conclusion is at odds with the DfT modelling and so raises questions about the validity of the NTM, which has been in use for over twenty years in a series of versions. The version cited in the new projections is NTM version 2 Rebased (NTMv2R), which is unexpected since a new version, NTMv5, was announced in 2019.

Modelling regressed

NTMv5 was developed as a spatially detailed model to complement NTMv2R by providing additional capabilities for assessing the impact of major new road schemes, packages of transport improvements or spatially based charging arrangements. One particular purpose was to develop scenario-based traffic forecasts arising from changes in population, travel trends, GDP, car ownership, fuel price and road tax. Accordingly, it is surprising that NTMv5 does not appear to have been used to generate the new traffic projections.

One possible explanation is that a peer review of NTMv5 by experienced practitioners made a considerable number of criticisms. The reviewers advised caution in application of the model, primarily due to the focus of the NTMv5 being on the more strategic highway network, whereas many of the potential applications relate to urban travel policy and public transport interventions. In particular, the reviewers were critical of the treatment of urban traffic, observing that the assumed relation between traffic speed and demand growth lacked validity, and that the range of policies aimed at reducing urban car use were not taken into account. Besides, it was noted that the DfT’s car ownership model has not recognised that ownership in dense urban areas has been declining for many years in response to increasing population density, notwithstanding rising incomes. The reviewers concluded that the model could not be safely used to examine policies that relate specifically to London, and queried whether this might apply more generally to rapidly growing dense urban areas across England. They took the view that the model should be suitable for use in forecasting the growth of road traffic in most areas other than those adjacent to or within major urban areas, which is a pretty major qualification.

So perhaps the DfT was unable to rectify NTMv5 to respond to these criticisms, and hence reverted to NTMv2R, which had previously been used to prepare the 2018 National Road Traffic Forecasts. This version was also the subject of peer review, the reviewers noting problems with modelling traffic in London and other conurbations where non-car modes are most competitive. The 2018 Forecasts predicted substantial traffic growth in London, but admitted that this was likely to be over-forecasting because travel behaviour in London and relationships between key variables and road traffic demand can be different to the rest of the country, due to a high use of public transport and significantly higher congestion on roads. This was recognised as known issue with the NTM, which it was intended would be addressed in the future (para 4.33 of 2018 forecasts). However, it is not clear whether this has been done, prior to preparation of the new projections.

There is bound to be feedback from congested road capacity to travel demand. In the ‘vision and validate’ approach, nowadays effectively adopted by cities, the vision of the balance between the twin functions of roads – movement and place – means that travel demand must be managed. This contrasts with the earlier ‘predict and provide’ perspective, where forecasts of traffic growth led to proposals to increase road capacity. If our vision now includes Net Zero, the presumption of increased road capacity is problematic, and the modelling should take account of capacity constraints on demand for road travel. Given that over 80% of the UK population live in urban areas, models need to be responsive to urban traffic conditions.

The validity of the NTM is therefore questionable. The modelling suite used to prepare the present projections is complex and opaque, hence it is not possible for those other than DfT modellers and their consultants to understand what has been achieved and what has not. The peer reviews provide an exceptional opportunity to look under the bonnet, and what was found make one doubt whether the NTM in its various versions is reliably roadworthy. And that’s before the problems associated with specifying scenarios to reflect policy uncertainties.

One intention in creating NTMv5 was to make this important model transparent to external stakeholders, which NTMv2R is not. Lack of transparency and accessibility contrasts unfavourably with the online Carbon Calculator of the Department for Business, Energy and Industrial Strategy, open to all.

Projecting future road traffic volumes is not an end in itself, rather it serves policy purposes. Projections of growth of both traffic and congestion delays would help justify a further major road investment programme. Projecting carbon reductions of 98% meets the Net Zero objective. Arguably, the modellers have struggled to reconcile both policy requirements, but have fallen short.

This blog was the basis for an article in Local Transport Today 24 January 2023.

Transport

The House of Lords Built Environment Committee is carrying out an inquiry into public transport in towns and cities. I was invited to submit written evidence, which is now published.

My conclusions:

For public transport in towns and cities to be improved, the share of car travel needs to be reduced, to lessen both competition for passengers and road traffic congestion.


To reduce car use, better public transport is needed, which requires both local government to take overall charge of services and to have a sustainable source of funding beyond the farebox.


There are no new technologies that will make much difference.

Car useEconomicsTransport

The Department for Transport (DfT) has started planning its third Road Investment Strategy (RIS3), a five-year investment programme for the Strategic Road Network (SRN) for the period 2025-2030. The approach is conventional – a programme of projects, with little overview of how societal objectives will be advanced by the likely substantial expenditure. Yet there are five major issues that need to be addressed for the programme as a whole.

First, there is a need to reconcile the government’s Net Zero objective with the carbon emissions from both the tailpipes of the additional traffic arising from increased road capacity and the embedded carbon in the cement, steel and asphalt used in construction. Recent presentations by the DfT’s Transport Appraisal and Strategic Modelling (TASM) division indicated an intention to tackle this issue at scheme level, but this is misconceived. What matters is the overall contribution of RIS3 to carbon emissions and how this is to be offset or otherwise justified.

Second is the question of how RIS3 advances the government’s Levelling Up agenda, where the recent, well-received White Paper identified twelve medium-term ‘missions’ to be pursued across all departments. The one specific to transport states: ‘By 2030, local public transport connectivity across the country will be significantly closer to the standards of London, with improved services, simpler fares and integrated ticketing.’ Although the rate of progress implicit in ‘significantly closer’ is vague, the direction of travel is clear and the objective is not in dispute.

There is no mention of investment in the SRN in the Levelling Up White Paper. This is appropriate since there is, if anything, an inverse relation between the performance of the road network and economic prosperity across the nation, given that delays on the SRN due to congestion are greater in London and the South East than in other regions of England.

The implication of the White Paper approach is that there should be a substantial switch of DfT funds from road investment to improve public transport beyond London, if the Department is to play a full role in supporting the government’s the Levelling Up agenda. Yet the Department’s recently issued Levelling Up Toolkit is essentially a pro forma for a box-ticking exercise aimed at justifying investments already forming part of agreed expenditure programmes. There is palpable inconsistency here.

Third, we have the problem of the safety of smart motorways. These require conversion of the hard shoulder to a running lane as an economical means of increasing capacity without the expense of rebuilding bridges. Generally, new roads are safer than older roads, which meant that adding road capacity yields a modest safety benefit. But this is not obviously the case for smart motorways, and there has been considerable pushback from the public and the House of Commons Transport Committee. As a result, the DfT has paused the roll out of new smart motorways until five years of safety data is available for schemes introduced before 2020. A decision on the generic safety of smart motorways will be an important factor in developing RIS3.

Fourth, and less recognised, there is a question about the economic benefits from additional road capacity. There are two published evaluations of smart motorway schemes where the traffic flows after opening were very different from those that had been forecast. For the M25 Junctions 23-27 scheme, the traffic flowed faster one year after opening but subsequently delays reverted to what they had been before opening on account of greater traffic volumes than forecast. For the M1 J10-13 scheme, traffic speeds five years after opening were lower than before opening. Since the main economic benefit of road widening is the saving of travel time, both schemes had negative benefit-cost ratios (BCR) at outturn.

Examination of the reports of the traffic and economic modelling of these two schemes showed substantial time-saving benefits expected for business users, offset by a small amount of increased vehicle operating costs (VOC) arising from additional traffic volumes. There were also time savings to non-business users (for commuting and other local travel) but these were entirely offset by increased VOC – because these were local trips that rerouted to the motorway to save a few minutes of time, at the expense of additional fuel costs.

The scope for rerouting local trips to take advantage of increased motorway capacity is likely to be underestimated in modelling. Local users have the flexibility to vary routes whereas long distance business users will stay on the motorway unless there is a major holdup. Moreover, the general use of digital navigation in the form of Google Maps and similar offerings makes choice of minimum time options commonplace.

Even when the outturn total traffic flows are a reasonable match to those forecast, the scheme economics could be much worse than predicted if there is more local traffic, and hence less long distance business traffic, than projected. Traffic and economic modelling involve recognition of different classes of road user with different values of travel time: cars, LGVs, HGVs, business, local commuters, and other local users. However, the monitoring of outturn traffic flows does not distinguish between these classes of users. GPS tracking make such distinctions possible.

The DfT has emphasised the importance of evaluation of outturns of investments. Yet the failure to appreciate the need to break total traffic flows down into the segments that had been modelled reflects a serious professional shortcoming. As a result, we cannot be at all confident that investments to increase SRN capacity do more than facilitate rerouting of short trips by local users, of nil economic value. Likewise, we do not have the kind of detailed evaluation data that would allow traffic models to be better calibrated for future use.

The fifth issue for RIS3 is that the widespread use of digital navigation by drivers prompts questions about the continued focus of DfT and National Highways on major civil engineering expenditure. Contrast the aviation sector, where new runways or terminals are occasional efforts, not regular business. The main focus of airlines and air traffic control is to improve operational efficiency, to sweat the assets employing the techniques of operational research. We have a mature road network in Britain. It’s time to focus on operational efficiency. Yet it seems not to occur the National Highways that working with Google Maps, TomTom and other providers of digital navigation services would be a cost-effective means of improving the performance of the network.

More generally, the DfT is trapped in its box labelled Transport Analysis Guidance (TAG), a thousand pages of prescription to which more text is added when some new issue or policy arises, such as Net Zero, Levelling Up, inequalities or gender. The task for those promoting a scheme is to tick all the boxes and flex the modelling to generate BCRs that represent good value for money. Evaluation of outturns is inadequate to distinguish between success and failure.

Although the DfT pays lip service to the need to think at the strategic level, the TAG framework does not facilitate this in that the detailed analysis is at project level. Other interested parties do not challenge the Department’s approach. The consultants and local authorities do not bite the hand that feeds them. The professional societies, institutions and think-tanks do not engage. The National Audit Office carries out good analysis of road investments on occasion, but not systematically. The Office for Rail and Road scrutinises the management of the SRN, including how well new investments are delivered, but does not see its role as enquiring into how investments benefit road users. This is quite unlike the regulators of other infrastructure industries – electricity, gas, water, telecoms – that are focused on how consumers benefit from investment.

The DfT is stuck in its box and seems unlikely to break out. The best bet for a strategic view of RIS3 may come from the National Infrastructure Commission, which has begun the development of its second National Infrastructure Assessment. The Commission’s advice was the basis of the government’s £96 billion rail investment programme for the North and the Midlands. This required fresh thinking about the benefits of transport investment at the level of the whole programme, an approach clearly needed for RIS3.

This blog post formed the basis of an article in Local Transport Today of 25 March 2022.

Transport

The House of Lords Environment Committee is carrying out an inquiry into public transport in towns and cities. I was asked to provide a submission, as follows.

The scope for public transport in cities and towns depends importantly on the level of car use, both because the car competes for passengers and because car traffic impedes the progress of buses, lessening their attractiveness.

The car is the dominant means of travel in Britain and other developed economies. It offers efficient door-to-door travel over short to moderate distances where traffic congestion does not lead to unacceptable delays and where parking is available at both ends of the journey. Public transport does not offer an attractive alternative to most car drivers in these circumstances. However, in urban areas where congestion causes delays and where parking is costly and limited, alternatives to car travel become attractive. To grow public transport use in towns and cities, it is necessary both to improve bus and rail services and constrain car use.

Urban travel and traffic

It is necessary to recognise that our availability of time always constrains the amount we can travel. There are many activities that we need to fit into the 24 hours of the day, and on average we spend just an hour on the move. This limits the build-up of road traffic congestion, which arises in areas of high population density and high car ownership where there is not enough road space for all the car trips that might be made. If traffic volumes grow for any reason, delays increase and some potential car users make other choices. We may change the timing or route of a car journey, or the travel mode where there are alternatives available, or a different destination such as an alternative shopping centre, or not to travel at all, for instance by shopping online.

Road traffic congestion is therefore self-limiting. We know from experience that we cannot build our way out of congestion by adding road capacity, since this allows previously suppressed car journeys to emerge, restoring congestion to the previous level. Conversely, if urban road space is taken away from cars in order to create bus or cycle lanes, then initially congestion will increase. But the additional delays will induce some car drivers to make alternative choices and congestion will revert to what it had been. The overall impact of reducing urban road space is to reduce the share of journeys by car.

Accordingly, it is difficult to reduce the intensity of traffic congestion, but it is possible to reduce the amount of congested traffic by reducing road space available to general traffic, which can be publicly acceptable if alternatives to the car are provided. This is what has been happening in London over many years, as the population has grown, as there has been large investment in public transport, and as there has been a reduction in road space available for cars. Private transport use fell from 48% of all trips in 2000 to 37% in 2019, while public transport use grew from 27% to 36% over the same period. Cycling increased from 1.2% to 2.4% while walking held steady at 25%. The London Mayor’s transport strategy, published in 2018, ambitiously aimed to cut private transport use to 20% of all trips by 2041.

Creating cycles lanes reduces the space available for cars but in itself it does not get people out of their cars. Copenhagen is a city famous for cycling, with 28% of journeys made by bike. Yet car traffic is only slightly less than in London. Aside from cycling, the other big difference is that public transport accounts for only half the proportion of trips compared with London. The experience of Copenhagen indicates that we can get people off buses onto bikes, which are cheaper, healthier, better for the environment and no slower in congested traffic. Yet buses are an efficient way of using road space to move people in urban areas, with diesel engines being replaced by electric or hydrogen propulsion to cut carbon emissions. We would like to get drivers out of their cars onto bicycles, yet this has proved difficult, even in Copenhagen, a small flat city with excellent cycling infrastructure and a strong cycling culture.

Looking across a range of European cities, we find very diverse patterns of journeys by the different travel modes, reflecting, history, geography, size and population density. But we do not find cities with high levels of both cycling and public transport.

Policy options for towns and cities

British cities tend to have lower population densities than European counterparts on account of our preference for low-rise housing with gardens; this means that public transport is harder to deliver cost-effectively. British cities vary considerably as regards use made of public transport. Two otherwise seemingly similar cities, Brighton and Bournemouth, have very different shares of commuting by public transport – 23% and 7% respectively. Nevertheless, there are two broad policy options available to all towns and cities, for local decision:

  • whether to push back the cars to increase street space for engagement by those on foot, with active travel and public transport as the alternative to the motorised mobility, as successfully implemented in London;
  • or whether to accommodate car travel, as has been the practice in the past and as remains popular with many residents.

Pushing back the car requires improving the public transport alternative. Urban rail is fast and generally reliable, but costly to implement. It can provide an attractive offering, as for instance London’s Overground, created from existing underused tracks, and Nottingham’s tram network where an extension was financed from the proceeds of the local Workplace Parking Levy. Bus Rapid Transit on dedicated traffic-free routes is a less costly alternative to new rail, for example the Cambridgeshire Guided Busway. Buses on roads with general traffic, whether in bus lanes or not, offer a less attractive alternative to motorists – a chicken-and-egg situation.

Integration of public transport across the modes increases its attractiveness, as do the innovations adopted in London, including cashless ticketing with daily or weekly capped charges, and extensive real-time information about services available through mobile phone and other devices. The ability of city regions to take responsibility for public transport, on the London model, will be an important means to improve public transport where adopted.

The recent well-received Levelling Up White Paper identified twelve medium-term ‘missions’ to be pursued across all departments. The one specific to transport states: ‘By 2030, local public transport connectivity across the country will be significantly closer to the standards of London, with improved services, simpler fares and integrated ticketing.’ Although the rate of progress implicit in ‘significantly closer’ is vague, the direction of travel is clear and the objective is not in dispute. However, as well as devolving relevant responsibilities to city regions, it will be necessary to allocate additional funds on a sustainable basis. The experience of relying on private sector bus companies has shown that a high level of service cannot be sustained by commercial financing.

It would be worth considering the example of the French ‘versement transport’, a hypothecated urban regional payroll tax levied on the total gross salaries of all employees of companies of more than 11 employees, which was originally intended to raise capital for investment in local public transport infrastructure, but is more and more used to cover its operating expenses.

New technologies

There are four new technological developments affecting road transport:

  • Electric propulsion, being adopted for buses, eliminates tailpipe emissions of pollutants and carbon, but does not otherwise change the nature of the service.
  • Digital platforms are having a big impact on retail businesses. For transport, booking of rail and air travel has been transformed. Ride-hailing, exemplified by Uber, has made a major impact on the taxi business. There have been trials of Demand Responsive Travel whereby smartphone apps are used to book a trip on a minibus that operates a flexible route to meet demand, but the economic viability of this mode is not yet generally established.
  • Digital navigation, typified by Google Maps’ routing recommendations, is changing how the road network is used, but is not relevant to buses on fixed routes.
  • Vehicle automation may offer the prospect of driverless buses, but whether this would be feasible in city traffic is far from clear, as is the cost of the technology and the support it might need. Driverless trains are possible on systems constructed for that purpose, such as the Docklands Light Railway, but an attendant rides on every train to oversee safety and security.

In short, it seems unlikely that public transport will be transformed by new technologies.

Summary

For public transport in towns and cities to be improved, the share of car travel needs to be reduced, to lessen both competition for passengers and road traffic congestion.

To reduce car use, better public transport is needed, which requires both local government to take overall charge of services and to have a sustainable source of funding beyond the farebox.

There are no new technologies that will make much difference.

Car useTransport

The Department for Transport’s National Transport Model (NTM) was first constructed two decades ago and has subsequently undergone a number of phases of development. The main function of the model has been to provide projections of travel demand as the basis for justifying investment in the road network. The model has also been used to project future carbon emissions, to inform the Department’s Transport Decarbonisation Plan, as well as to explore the impact of technological developments such as electric vehicles.

An account of the latest version, effectively a new model known as NTMv5, was released recently in the form of a 250-page ‘Quality Report’, oddly, two years after completion. NTMv5 is a spatially detailed conventional four-stage transport model structure, iterated so that congestion feeds back into demand. The model has been implemented using the standard commercial software, PTV Visum. The intention is that the model should be transparent to external stakeholders, a very welcome development given the opacity of previous versions of the NTM. The complexity of the model means that a single run takes around ten hours, with a number of iterations needed to achieve convergence of outcomes.

However, there are some notable limitations to the model. There is no detailed treatment of public transport capacity. Car ownership data derives from a separate model, which has not been updated. And the primary source of growth of travel demand is the DfT’s National Trip End Model data set that projects expected changes in demography and land use, which are problematic of account of uncertainty of economic growth, population growth and distribution, and planning policy.

A number of potential applications of the model have been identified, of which the most immediate is the preparation of new national road traffic forecasts. Also recognised is a need to project future transport carbon emissions, and for the analysis of packages of road schemes at national level, including value for money.

The purpose of the succession of NTM versions has been to support the traditional ‘predict and provide’ approach to road investment. This viewpoint persists in the latest version where the stated rationale for analysis of packages of road schemes is to identify ‘gaps in the network… where the road capacity in future may be insufficient, leading to unacceptable rises in congestion and journey times.’ (section 2.4.2). Yet we do not adopt that approach when considering urban roads, and the scope for enlarging peri-urban motorways at acceptable cost by converting the hard shoulder to a running lane is now problematic on account of public concerns about safety. Besides, the scale of induced traffic has been persistently under-estimated in traffic modelling, so the aim of avoiding unacceptable congestion seems naïve, even before addressing the Net Zero objective.

The model builders struggled to treat the complexities of urban traffic. It was accepted that a full link-based modelling of urban road capacity and related journey time responses could not be achieved, and therefore a simplified approach had to be applied. This involves assuming general fixed speeds on urban networks for the Base Year, which were reduced over time based on assumed growth of demand. (sections 4.7 and 11.4). This simplification has implications for projections of traffic in London, as recognised by the peer reviewers.

Peer Review

The DfT has published a Peer Review and an Audit of NTMv5. The 120-page peer review, led by the seasoned practitioners John Bates and Ian Williams, drew attention to a number of apparent shortcomings in the methodology (too technical for me to appreciate sufficiently to offer comment). These led to counterintuitive results when sensitivity tests were run, notably for London.

The reviewers advise caution in application of the model, primarily due to the focus of the NTMv5 being on the more strategic highway network, whereas many of the potential applications focus on urban travel policy and public transport interventions. In particular, the reviewers are critical of the treatment of urban traffic, observing that the assumed relation between traffic speed and demand growth lack validity, and that the range of policies aimed at reducing urban car use are not taken into account. Besides, it is noted that the DfT’s car ownership model has not recognised that ownership in dense urban areas has been declining for many years in response to increasing population density, notwithstanding rising incomes.

The reviewers find that for London, the model results are not convincing. The observed car (driver + passenger) trip mode share is 38% from the National Travel Survey in 2015/16, whereas that in the model in 2015 is 50%. Moreover, the model projects a future gain of car share, whereas over the period 2005-16 a major decline of 5.6% was observed (para 4.3.5). The reviewers concluded that the model could not be safely used to examine policies that relate specifically to London, and query whether this relates more generally to rapidly growing dense urban areas across England. They took the view that the model should be suitable for use in forecasting the growth of road traffic in most areas other than those adjacent to or within major urban areas (section 6.3.24), which is a pretty major qualification.

Audit

The 260-page audit of NTMv5, carried out by consultants Arup and AECOM, drew attention to a number of shortcomings in both documentation and substance, including that some of the model components and tools used to process the data are not owned by the Department, which limited access to some of the key processes and data used in model development – not consistent with the aim of transparency to external users. The auditors advised that users of model outputs should be cautious because of problems in reaching convergence to a stable outcome as the model is run through repeated iterations, a concern also of the peer reviewers.

What next?

The NTM documents recently published are two years old. No doubt, further development of the model has been taking place to respond to the issues raised in peer review and audit. In its Transport Decarbonisation Plan published last July, the DfT stated its intention to review the National Policy Statement on National Networks, the basis of strategic planning of road and rail investment, and to update the forecasts on which it is based. NTMv5 will presumably be used for this purpose. Yet the modellers will be stretched to meet the divergent needs of their client policy makers, between bullish forecasts of travel demand to justify continued infrastructure investment and bearish projections of transport carbon emissions. Given the uncertainties of the model illuminated by peer review and audit, it will be hard to be confident about the validity of carbon forecasts out to 2050 and 60-year investment appraisals.

While the DfT’s intention to make NTMv5 available for use beyond the Department is praiseworthy, this seems problematic in practice. Doubtless the large transport consultancies could master the software and data, but given their complexity, clients would need deep pockets to fund the work. That would rule out non-government bodies that might want to challenge particular schemes. Regional transport undertakings have their own bespoke models. I am not aware of any academics who would be likely to buy into the NTM, a situation unlike national energy modelling where government and a substantial group of university researchers work with the same model. The DfT would be well advised to support academic researchers and others wishing to use NTMv5 to explore a range of policy scenarios.   

This blog was the basis for an article in Local Transport Today of 11 March 2022.

Car useTransport

The Office of Rail and Road has extensive responsibilities for regulating the largely private sector rail industry but quite limited oversight of public sectors roads. The Department for Transport is planning its third Road Investment Strategy investment programme (RIS3). The ORR has been consulting on its role in relation to RIS3. Essentially, the ORR sees its role as ensuring that National Highways (formerly Highways England) achieve value for money in implementing the DfT’s investment priorities.

The ORR consultation document states that it is not the role of the ORR to set roads policy or determine investment priorities. However, it is a shortcoming of the ORR’s approach that it does not consider to what extent the investments agreed by government achieve the benefits to road users that are expected. This is a major gap in public oversight.

The National Audit Office from time to time evaluates benefits to users of road investment, for instance its 2019 report on improvements to the A303. But NAO oversight is occasional, not systematic.

Detailed analysis of the outcomes of road investment may show major discrepancy between forecast and outturn, for instance for widening the M25 between junctions 23 and 27. One general explanation is the underestimation of the scale of induced traffic . Induced traffic reduces travel time savings, supposed main economic benefits of investment, which is why transport models tend to underestimate its magnitude.

One source of induced traffic is the rerouting of local trips, such as commuting, to take advantage of faster travel on widened motorways, pre-empting capacity intended for business users and so undermining the economic case for widening. This is likely to be a general phenomenon in or near areas of high population density, where the strategic road network comes under greatest stress, and where the case for additional capacity seems strongest.

More generally, average travel time, as determined in the National Travel Survey, has remained essentially unchanged for half a century, during which time huge sums have been invested in road infrastructure justified by the saving of travel time. Travel time savings are short-run. In the longer run, over the greater part of the life of the assets, the main benefit of investment that allows faster travel takes the form of increased access to people and places, opportunities and choices.

All in all, there is reason to suppose that the outcomes of road investments may be substantially different from that forecast by the traffic and economic models in use, and that road users are not benefiting from investment in new capacity to the extent intended. The ORR should take on the task of ensuring that road investment appraisal methodologies are fit for purpose.