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.

The Prime Minister’s recent announcement that the HS2 rail line will not now continue from Birmingham to Manchester and beyond raises issues both immediate and long term. Immediately, there is the question of how that money saved is to be reallocated. In the longer term, the question is whether we have an analytical framework that is both sufficiently complete and robust to be relevant to major projects whose gestation and implementation may span decades.

The Prime Minister’s principal stated reasons for scraping the lines beyond Birmingham were cost escalation, delays to construction, and the impact of Covid on travel behaviour. The money saved would be devoted to improved transport schemes outside London, mainly in the Midlands and the North of England, he argued. He also pointed to the huge chunk of the national transport investment budget taken up by HS2, for which Rishi Sunak implied was a relatively narrow user base and geography.

Certainly, the cost estimates of HS2 have grown substantially since the scheme was first announced in 2010. The initial cost of the full Y network, comprising both the first section to Birmingham and 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 is exposed.

The economic benefits projected in the Full Business Case were largely to rail users, predominantly £39 billion (present value, 2015 prices) as a result of reduction of train journey times. There were also significant benefits from reduction in crowding on the conventional network, as well as reduction in waiting and greater reliability as the network was enlarged by adding the new line, which, together with some smaller benefits, yielded net transport user benefits of £74 billion. To this was added benefits from agglomeration and other wider impacts to reach £94 billion net benefits. Taking into account revenues from fares resulted in a benefit-cost ratio (BCR) declared in 2020 to be 1.5, categorised as low-to-medium value for money.

Clearly, any further cost escalation since 2020 was potentially likely to tip the BCR into low value territory, a most unwelcome position for the largest single UK transport infrastructure project ever. But do the estimates of benefits reflect the reality? We need to go back to the core proposition, endorsed by the main political parties.

The stated intention of HS2 was to reshape the national economy by joining up the North, Midlands and London, effectively halving the journey times between the centres of the UK’s largest cities. This, it was contended, would allow businesses to invest beyond London whilst still retaining ready access to it. It was argued that the scheme would contribute towards sustainable growth in towns, cities and regions across the country, spreading prosperity and opportunity more evenly, acting as a catalyst for job creation, the development of new homes and ultimately, the regeneration of major cities and towns along the route.

This thinking was more heroic than business-like. The assumption of conventional economic investment appraisal is that the transport user benefits provide a good estimate of the ultimate benefits that arise as perfect markets redistribute benefits amongst the various beneficiaries, including land and property owners who gain from the improved access, the businesses that occupy the new premises, and people who occupy new homes. This itself is an unrealistic assumption in general. Moreover, in the case of HS2, for which the distribution of benefits between London and the cities of the Midlands and the North is crucial, estimation of spatial distribution was not attempted in the economic appraisal of the investment – and indeed is a difficult matter to predict.

Consider, for instance, a business with headquarters in London and a branch office in Birmingham. It might take advantage of the faster rail connection offered by HS2 to close the branch office, serving clients in Birmingham from London; or it might expand the Birmingham branch where office rents and housing costs are lower, on the basis that staff could get up to the head office speedily as necessary; or arrangements may be left unchanged, staff benefiting from the faster business travel spending more time in the office; and, of course, the increase in working from home as a result of the pandemic must influence all the possible business decisions. What might emerge could be an instance of what is known as the Two-way Road Effect, whereby improved accessibility between two regions may benefit prosperous areas rather than the poor areas targeted by the scheme, sucking activity away rather than bringing it in.

Given that the intention of HS2 has been to boost the economies of cities and region to the north of London, uncertainty about distribution of economic benefits means that the value of the investment was always hard to judge. Much would depend on the ability of the connected cities to take advantage of the new rail route to put in place city-centre development around new stations plus local transport infrastructure to speed travellers to and from their final destinations beyond the rail terminal. These longer origin to destination considerations can change to value of the high speed rail journey itself. The HS2 Full Business Case included an annex outlining hoped for developments around the new Curzon Street station in Birmingham, which illustrated the economic possibilities. But these did not constitute part of the economic case for the investment, to avoid double counting travel time benefits. This illustrates how notional time savings are tenaciously preferred to estimates of real-world benefits when applying the orthodox methodology to the appraisal of transport investments.

The inadequacy of the economic analysis, likely involving underestimation of the benefits from development, may well have contributed to the truncation of the HS2 project, given the latest BCR estimate of 0.8-1.2 quoted by the DfT.

A comparison with Crossrail

Another major rail investment that ran over time and budget was London’s Crossrail, renamed the Elizabeth Line on opening. Fortunately, those responsible kept their nerve. The project was not skimped or cancelled and has proved to be a great success, an example of a modern metro whose performance and popularity has surpassed expectations. The case for investment was based on the value of travel time savings to users (business, commuting and leisure) plus a number of wider economic impacts (mainly agglomeration benefits). The value of time saving benefits was put at some £12 billion, while the wider impacts provided an additional £7 billion in 2005. Subsequently, further analysis in 2018 increased the wider benefits to £10-£15 billion.

As with HS2, there was no explicit reference in the appraisal to the impact of the new rail route on real estate values or on the economic value of the businesses to be accommodated in new developments along the route. The assumption was that the boost to development and employment was accounted for by the value of travel time savings plus the wider impacts, an assumption that is implausible to non-economists. The economic analysis of the investment case failed to consider the spatial distribution of benefits, although by the very nature of the project, these would be largely within London. Nevertheless, the benefits to businesses were recognised by a funding agreement between the Mayor/TfL and the Government, which identified contributions of £300m from ‘developer contributions’ and a further £300m from a ‘London Planning Charge’ (subsequently to become the Mayor’s Community Infrastructure Levy or MCIL), a useful but not decisive contribution.

Transport for London has developed a framework to evaluate the benefits of the Crossrail investment. It is envisaged that a study to be published two years after opening will address the transport effects of the new railway, including: mode shift from cars to public transport, relief of congestion on public transport and roads, and the implications for air pollution and carbon emissions. A subsequent study is planned to consider the broader social and economic effects, including the effect of improved connectivity on new homes and jobs, changing patterns of employment and land use, and residential and commercial property prices. A report has already been published on the pre-opening impacts of Crossrail on property prices, arising from the announcement of the project; this found fairly small positive increases to both house prices and office rents.

TfL’s approach to evaluation is admirably ambitious, yet there is obvious inconsistency with the original investment case based on the value of estimated travel time savings and of wider impacts inferred from econometric analysis. It seems unlikely that it will possible to compare forecast and outturn by deducing time savings and agglomeration benefits from the evaluation findings. This prompts the question of whether, with hindsight, the investment appraisal could have been based on projections of the actual benefits that are expected to be achieved. Certainly, inconsistency of economic analysis as between appraisal and evaluation does not make much sense, not least because ex ante travel time savings and wider impacts are, by their nature, notional not observable.

A comparison with the Northern Line Extension

The possibility of forecasting the actual expected benefits of investment is illustrated by another London rail investment, the Northern Line Extension to a large brownfield site comprising the derelict Battersea Power Station and adjacent erstwhile low value commercial buildings and opportunity sites. The developers took the view that the optimal commercial gain would result from access to new properties on the site by means of an extension to the Underground, rather than by enhanced surface modes. The Battersea developers were therefore willing to contribute a quarter of the construction cost in cash. The Treasury agreed that additional taxes paid by businesses locating to the area would contribute the remainder of the financing of the rail link. On that basis, TfL could agree to proceed with construction, a rare instance of the capture of increased land value arising from new transport infrastructure to finance that infrastructure. Views may differ about the quality and coherence of the subsequent development, yet a significant area of central London has been transformed from low value to high value property, including a new building for the US Embassy.

It is relevant that there had earlier been a standard economic appraisal of transport user benefits for a range of alternative property and transport investments on this site, where the predominant benefits were travel time savings. It was found that extension of the Underground would have a less favourable benefit-cost ratio than other transport alternatives on account of the higher capital cost. Nevertheless, the decision was made to extend the Tube, the increase in real estate value being the deciding factor. Thus, much as with earlier development of the Underground, for instance the pre-war extension of the Metropolitan line, the decision was taken essentially on a commercial basis, with the estimated increase in real estate value forming an integral element of the investment decision. This exemplifies the scope for a transport authority working with a developer to take into account the value of real estate improvement for mutual benefit to take into account the increase in real estate values. In this case, of an underground electric railway, detrimental externalities were not important beyond the construction phase.


The main message from these reflections is that there are fundamental shortcomings to orthodox transport investment appraisal, as set down in the Department for Transport’s Transport Analysis Guidance (TAG). These arise principally from a requirement to requirement to estimate economic benefits based predominantly on time savings and other user benefits that are notional, not real and observable; the disregard of changes in land use and value that results from the improved access made possible by transport investment; and the lack of any mechanism to recognise the spatial and demographic distribution of benefits, a crucial concern in the context of regional disparities and avowed intentions to level up society. As exemplified by the cases discussed above, the orthodox approach is not fit for purpose and is becoming irrelevant for decisions making. This leaves political and commercial actors to call the shots.

These shortcomings are all the worse, given that there has been emphasis in the last two years, both in the Treasury’s Green Book and in TAG, on articulating the strategic case for a transport investment. The requirement is to set out a robust case for change that demonstrates how a proposal has a strong strategic fit to the organisation’s priorities and government ambitions. There were successive attempts to do this for HS2, clearly none wholly convincing, leaving observers with a feeling that the goal posts were being continuously moved. And now, consequent to cancellation, there is little sense of any strategic thinking, informed by cogent economic analysis, in the mishmash of investments and interventions announced by the Prime Minister, seemingly to avoid being accused of truncating HS2 merely to save money, and perhaps to find a more politically acceptable set of beneficiaries in the short term.

It is time for the DfT economists to desist from engaging in the incremental development of their thousand pages of TAG. Rather, they need to stand back and ask what purpose is being served by this, when decision makers evidently have quite unrelated preoccupations. The necessary shift in mindset is to recognise that the role of transport investment in generating economically transformational change depends on interlinked decisions by local political leaders, planners, developers and transport authorities, as illustrated by the Northern Line Extension. Appraisal needs to take a holistic view of economic benefits, including from development. The current methodological practice of focusing on transport user benefits in the absence of such linked decision-making means that the uncertainties about ultimate economic benefits are either too great to allow funds to be committed in the first place, or risk having the plug pulled after construction has started if costs increase, as illustrated by HS2.

The above blog was the basis for an article in Local Transport Today of 17 October 2023.

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.

Artificial Intelligence (AI) is much in the news. The development of Large Language Models (LLMs) has been crucial to recent advances. These are general purpose models based on artificial neural networks that can be trained on large quantities of unlabelled text using self-supervised learning. The breakthrough came from OpenAI, a US company originally set up to develop open source software, but which received $10bn investment from Microsoft so may be shifting to a more commercial mode of operation. For the moment at least, ChatGPT, its basic offering, is available without charge ( ).

There has been a full range of claims about this advance in AI, from offering a step change increase in productivity, which is why the prime minister wants Britain to lead the world, to concerns from knowledgeable experts that it would allow bad people to do bad things, or worse. So I thought it would be interesting to see what ChatGTP could do in practice. I posed two initial questions, and show the answers in full:

Q1 What are the causes of road traffic congestion?

‘Road traffic congestion can be caused by various factors, including:

  1. High volume of vehicles: An excessive number of vehicles on the road can lead to congestion, especially during peak travel times. As the number of vehicles increases, the capacity of the road may be exceeded, resulting in slower speeds and increased delays.
  2. Inadequate infrastructure: insufficient road capacity, poorly designed intersections, narrow lanes, lack of alternative routes, and inadequate public transportation systems can contribute to traffic congestion.
  3. Traffic incidents and accidents: Road accidents, breakdowns, and other incidents can disrupt the flow of traffic and cause congestion. When lanes are blocked or vehicles are immobilized, it can lead to significant delays.
  4. Roadworks and construction: Construction activities, maintenance work, and road repairs often require the closure of lanes or the diversion of traffic. These temporary disruptions can cause congestion, especially if they are not well managed or scheduled during off-peak hours.
  5. Traffic signal timing: Inefficient traffic signal timing can lead to congestion. If signals are not properly synchronized or do not consider the actual traffic demand, it can result in stop-and-go traffic patterns and delays.
  6. Bottlenecks and chokepoints: Certain sections of roads, such as narrow bridges, tunnels, or interchanges, may have limited capacity and create bottlenecks. When traffic volume exceeds the capacity of these areas, congestion can occur.
  7. Lack of public transportation options: In areas where public transportation is limited, unreliable, or inconvenient, more people rely on private vehicles, which can contribute to traffic congestion.
  8. Traffic management and planning: Inadequate traffic management strategies, including poor coordination between traffic control systems, insufficient signage, and improper lane markings, can exacerbate congestion.
  9. Special events and holidays: Large gatherings, festivals, sporting events, or holiday periods can generate additional traffic and cause congestion, especially if the road network is not prepared to handle the increased demand.
  10. Driver behaviour: Aggressive driving, lane weaving, improper lane changes, and lack of adherence to traffic rules and regulations can disrupt the flow of traffic and lead to congestion.

It’s important to note that the causes of traffic congestion can vary based on location, time of day, and other local factors. Addressing congestion often requires a multi-faceted approach involving infrastructure improvements, traffic management strategies, and promoting alternative transportation options.’

Q2 What is the best way to reduce road traffic congestion?

‘Reducing road traffic congestion requires a combination of strategies that focus on improving infrastructure, promoting efficient transportation systems, and encouraging behaviour change. Here are some effective approaches:

  1. Improve public transportation: Enhancing public transportation systems, such as buses, trains, and trams, can provide people with reliable and convenient alternatives to driving. This includes increasing the frequency and coverage of services, improving the quality of vehicles, and integrating different modes of transport.
  2. Encourage carpooling and ridesharing: Promoting carpooling and ridesharing programs can reduce the number of vehicles on the road. Incentives like preferential parking or reduced tolls for carpoolers can encourage more people to share rides.
  3. Implement congestion pricing: Congestion pricing involves charging fees for driving in congested areas or during peak hours. By making it more expensive to drive during times of high demand, it encourages people to shift their travel times or modes, reducing congestion.
  4. Develop and promote active transportation: Creating infrastructure for pedestrians and cyclists, such as sidewalks, bike lanes, and bike-sharing programs, can encourage people to choose walking or cycling for shorter trips. This reduces the number of vehicles on the road and eases congestion.
  5. Enhance traffic management and signal coordination: Optimizing traffic signal timing and coordinating signal systems can improve traffic flow and reduce congestion. Advanced technologies, such as adaptive signal control systems, can adjust signal timings based on real-time traffic conditions.
  6. Invest in road infrastructure: Expanding road capacity, building additional lanes, and constructing new roads in areas with high congestion can increase the overall capacity of the transportation network. Additionally, improving road design and addressing bottlenecks can help alleviate congestion.
  7. Implement smart transportation systems: Intelligent transportation systems (ITS) use technologies like real-time traffic monitoring, dynamic message signs, and navigation apps to provide drivers with information about traffic conditions and alternative routes. This helps drivers make informed decisions and reduces congestion by distributing traffic across different routes.
  8. Encourage telecommuting and flexible work hours: Promoting telecommuting and flexible work hours can reduce peak-time traffic by allowing employees to work from home or choose non-peak hours for commuting. This can help spread out the traffic demand and alleviate congestion during rush hours.
  9. Develop land-use planning strategies: Efficient land-use planning can reduce the need for long commutes by locating residential areas closer to workplaces, schools, and amenities. This reduces overall travel distances and decreases congestion.
  10. Promote behaviour change and education: Encouraging responsible driving behaviour, such as obeying traffic rules, avoiding aggressive driving, and practicing eco-friendly driving techniques, can help improve traffic flow and reduce congestion. Public awareness campaigns and educational programs can play a role in promoting these behaviours.

It’s important to note that no single solution can completely eliminate traffic congestion. A combination of these strategies, tailored to the specific needs and characteristics of each location, is typically the most effective approach to reducing road traffic congestion.’

I was impressed by these pretty good summaries of conventional wisdom. They lack penetrating insight and do not cite sources, but each would serve as a useful summary, perhaps as an introduction to a substantial analysis, for an article by a non-specialist journalist, or as the basis for a student essay. ChatGPT looks to be a real competitor for Google and Wikipedia, and indeed Google has entered the field with its own offering, known as Bard.

However, the limits of ChatGPT can be illustrated by a further question:

Q3 What do you know about David Metz, Centre for Transport Studies, University College London?

‘David Metz is a prominent transport expert and researcher associated with the Centre for Transport Studies (CTS) at University College London (UCL). He has made significant contributions to the field of transport planning and policy over the course of his career.

David Metz has an extensive background in transportation and urban planning. He obtained his Ph.D. in Transport Economics from UCL and has since held various academic positions, including Professor of Transport Studies at UCL and Honorary Professor at the Institute for Transport Studies, University of Leeds.

At the Centre for Transport Studies, David Metz has conducted research on a wide range of transport-related topics, including travel behaviour, sustainability, transport policy, and the relationship between transport and climate change. His research often focuses on understanding the complex interactions between transport, society, and the environment.

David Metz is known for his critical analysis of transport policies and his ability to challenge conventional thinking. He has emphasized the importance of considering the social and behavioural aspects of transport planning and policy-making, highlighting the need to move beyond purely technical solutions.

In addition to his research work, David Metz has been involved in advisory roles and has provided expert advice to governments and organizations on transport policy matters. He has served on various committees and panels, including the UK Sustainable Development Commission and the Scientific Advisory Committee of the UK Department for Transport.

David Metz’s contributions to the field of transport have been recognized through numerous awards and honours. He is a Fellow of the Academy of Social Sciences and has received the Wolfson Prize for Transport Policy. His research publications, including books and academic papers, have made a significant impact on the field and are widely cited by transport professionals and researchers.

Overall, David Metz is a respected figure in the field of transport studies, known for his research on transport policy, sustainability, and the social dimensions of transportation. His work at the Centre for Transport Studies, UCL, has contributed to advancing knowledge and understanding in the field of transportation.’

This is all very flattering. However, key ‘facts’ are quite wrong. I do not have a PhD in transport economics. I have not had an affiliation with the University of Leeds. I have not served on the UK Sustainable Development Commission or the Scientific Advisory Committee of the UK Department for Transport. I am not a Fellow of the Academy of Social Sciences and have not received the (non-existent) Wolfson Prize for Transport Policy. Regrettably, I have not received ‘numerous awards and honours’.  It would be going too far to say that my books and papers are widely cited by transport professionals and researchers. And my one small claim to fame, that I was Chief Scientist at the Department for Transport, was overlooked.

What is the origin of these ‘hallucinations’, as they are known – apparent confident responses not justified by the data on which the model was trained? This training presumably did not include data from a simple Google search that would have generated real facts, or a check with Amazon to find the books I have authored, or a check with LinkedIn for my career. The origin of such hallucinations remains a mystery since the LLMs are not open for inspection or are capable of validation. Nor, evidently, do they have a built-in fact checker.

So, we cannot yet dispense with Google as a source of citations, ranked according to impact, nor with Wikipedia with its editorial oversight of contributions. But Chat GTP and similar AI offerings can offer plausible narrative outlines that should be checked for factual accuracy. And they may improve over time.

One further Q&A for many readers of this blog:

Q4 How to be a better transport planner?

‘To become a better transport planner, consider the following steps:

  1. Gain Knowledge and Expertise: Develop a deep understanding of transportation systems, including various modes of transport, infrastructure, policy frameworks, and relevant technologies. Stay updated with the latest trends and innovations in the field. Pursue formal education or certifications in transportation planning or related disciplines.
  2. Analyze Data: Transportation planning involves analyzing vast amounts of data. Learn to use data analysis tools and software to extract insights from transportation surveys, traffic counts, travel demand models, and other relevant sources. Apply statistical methods and modeling techniques to interpret data accurately.
  3. Understand Stakeholder Needs: Recognize the importance of stakeholder engagement. Collaborate with various stakeholders, such as government agencies, urban planners, community organizations, and transportation providers. Understand their needs, concerns, and aspirations to develop effective transport plans that address their requirements.
  4. Consider Sustainability: Promote sustainable transportation solutions that minimize environmental impact, enhance public health, and prioritize energy efficiency. Integrate strategies for reducing emissions, improving air quality, and promoting active transportation modes like walking and cycling.
  5. Plan for Multimodal Systems: Design transportation systems that accommodate multiple modes of transport, including private vehicles, public transit, walking, and cycling. Aim to create an integrated and seamless network that offers efficient connectivity between different modes and encourages modal shift.
  6. Embrace Technology: Keep up with advancements in transportation technology, such as intelligent transportation systems, autonomous vehicles, and mobility-as-a-service (MaaS) platforms. Understand how these technologies can enhance transport efficiency, safety, and accessibility.
  7. Conduct Impact Assessments: Evaluate the potential impacts of proposed transportation projects or policies. Assess their effects on traffic flow, travel times, air quality, land use, and social equity. Use impact assessment tools and methodologies to inform decision-making and mitigate any adverse consequences.
  8. Collaborate with Other Disciplines: Work closely with urban planners, engineers, architects, and environmental specialists to develop holistic and comprehensive transport plans. Emphasize interdisciplinary collaboration to integrate transportation planning with land use planning, urban design, and environmental sustainability.
  9. Engage in Continuous Learning: Participate in professional development activities, attend conferences, workshops, and seminars related to transportation planning. Stay informed about emerging research, best practices, and policy updates. Actively seek feedback and learn from the experiences of other professionals in the field.
  10. Advocate for Positive Change: Act as a catalyst for change by advocating for sustainable and equitable transportation policies and practices. Engage in public outreach, education, and advocacy to promote awareness and support for transportation initiatives that benefit communities and enhance quality of life.

Remember that becoming a better transport planner is an ongoing journey. Continuously refine your skills, stay open to new ideas, and adapt to evolving societal needs and technological advancements in the transportation sector.’

So there you have it. Who could argue?

This blog was the basis of an article in Local Transport Today of 3 July 2023.

The economic benefits of agglomeration – learning, sharing and matching – have long been recognised as driving the growth of cities. In conventional transport economic analysis such benefits comprise the main part of the ‘wider impacts’, over and above transport user benefits. This process of concentration of economic activity in city centres has been in part a consequence of the shift of economic activity from manufacturing to business services, and has taken place despite the development of information and telecommunication technologies in recent decades that has allowed remote working. The inference has been that the positive benefits of agglomeration have outweighed the negative aspects such as higher rents and commuting costs.

The coronavirus put this inference to the test. Many employees who did not need to deal with clients face to face successfully worked from home and have proved reluctant to return full time to the workplace, not least because the successful development of broadband and Zoom, Teams etc for remote meetings. This is leading to changes in the demand for city centre office space, for instance at Canary Wharf in London’s Docklands.

We have seen a previous technological development that shifted the balance between the centripetal and centrifugal forces underlying observed agglomeration clusters. Fleet Street 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 which 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. However, 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 be disbursed to scattered locations around London. Nowadays, ‘Fleet Steet’ is a metaphor for the newspaper industry, no longer to 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 is whether advances in technology and the experience of the pandemic have led to a tipping point in what had seemed to be a continuing process of city centre concentration, so that a more dispersed pattern of economic activity will develop. It will take time to see what use is made of the space freed up by major businesses leaving Canary Wharf and downsizing office accommodation. Possibly lower rents may attract other businesses that previously could not afford central locations. Repurposing is also possible to create residential accommodation, hotels, laboratory space and the like. The implications for travel demand and supply take time to become clear. It is paradoxical that firms are leaving Canary Wharf just when the opening of the Elizabeth Line has improved its connectivity to central London and to Heathrow.

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 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.

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.