The Mayor of London published a draft Transport Strategy in June. The consultation period has just finished. Generally, the draft is sensible in its intentions, emphasising the important aims of healthy streets and people, good public transport, and accommodating a growing population and economy.

One stated objective is to achieve 80% of all trips by walking, cycling or public transport by 2041. However, while reduction in the share of journeys by car is desirable, it would be very ambitious to achieve this aim.

Car mode share has been falling in London, from 50% of all trips (driver and passenger) in 1993 to 36% in 2015. I projected  that on existing policies it would fall to about 30% by 2040. This is happening because the capacity of the road network prevents traffic growth, and population growth therefore results in a decline of car mode share. However, a reduction to 20% car mode share of trips could be difficulty for the following reasons:

  • Walking in London has remained at 24% of all trips consistently for the past 20 years. Walking is the slowest mode, other than for very short journeys, and could therefore be difficult to increase.
  • Cycling is growing, but from a low base. However, it is difficult to get people out of cars onto bikes. Copenhagen has excellent cycling infrastructure and a strong tradition of cycle use, which comprises 30% of all trips. However, car use at 33% is not very different from London. Walking and public transport use are much lower than in London. Crowding on public transport is likely to be reduced by promoting cycling, but there may not be much impact on car use.
  • Growth of bus use will tend to be constrained by traffic congestion, and growth of rail use by crowding and the cost of investment in new routes.
  • Reducing carriageway available for cars, for instance by allocating more road space to pedestrians and to bus and cycle lanes, would tend to reduce car use, but would not reduce congestion and would be detrimental for goods deliveries.



Transport for London has refused to renew Uber’s licence as a private hire operator after expiry of its current licence on 30 September, on the grounds that Uber lacks corporate responsibility in relation to a number of issues that have potential public safety and security implications (more detail available). Uber is appealing against this decision. Thus far more than 700,000 people have signed an online petition in support of Uber.

The Mayor, Sadiq Khan, has endorsed TfL’s decision, but has recognised the popularity of Uber and has said that there is a place in London for all private hire companies that play by the rules and that he wants to help support innovative businesses in London and to create a vibrant and safe taxi and private hire market. The Mayor is consulting on his draft Transport Strategy, which has the ambition to reduce car use to 20% of all trips by 2040. One reason why car ownership and use in London is on a downward trend is that there are alternatives to the private car, Uber and the like as well as buses and trains.

3.5m Londoners use Uber via its smartphone app and more than 40,000 licensed drivers work for the company. While there have been criticisms of a number aspects of aspects of Uber’s operations, it is evident that this innovative service meets a real mobility need. Its virtues include the clear location and timing of the arriving vehicle with a named driver, the ability to rate the driver after the trip, no need to pay by cash or card, and applicability of the same app throughout London and to all cities that Uber serves. These attractions, together with relatively low fares, account for the success of Uber in competition with black cabs and local minicabs.

TfL’s refusal to renew Uber’s licence on grounds of safety and security seems at odds with the popularity of the service amongst Londoners. Uber must have a fair chance of modifying the decision on appeal to the court or in negotiation. But if not, others will seize the opportunity to step in. The drivers and their cars are there, as are the smartphones waiting to be loaded with new apps. There are other platforms in London such as Gett and mytaxi, (both for black cabs at present), and it is reported that Uber’s main competitor in the US, Lyft, is thinking about coming to London.

An important question is whether a single platform would tend to be dominant on account of economies of scale and scope – spreading the overhead costs across the greatest number of users and providing the fastest response times. Or whether stable competition between a number of providers could be achieved, as they compete for both clients and drivers by offering attractive terms to both. Lyft has been growing market share in New York at Uber’s expense. The New Economics Foundation has proposed ‘Khan’s Cars’, a mutually-owned, publicly-regulated alternative to Uber.

Another question is the sustainable level of fares for services provided by these platforms, which would need to be sufficiently high to attract drivers but low enough to be competitive with conventional taxis and minicabs. The app-based platforms such as UberPool allow customers to share journeys with other going in the same direction at lower fares – a source of competitive advantage as well as a means of increasing vehicle occupancy, which is helpful for efficient use of the road network.

For the longer term, the possibility of driverless vehicles offers scope for substantial cost reduction for robotic taxis. This could allow population of the vacant space between high capacity, low fare public transport offering stop-to-stop or station-to-station service, and low capacity, high fare taxis offering door-to-door journeys.








The National Infrastructure Commission has sought evidence on how the deployment of intelligent traffic systems could help optimise the road network. I sent a response, found here Metz NIC traffic management 1-9-17

My argument is that we need to move beyond traffic management using traffic signals to management involving collaboration between public sector road authorities and the private sector suppliers of digital maps and route guidance apps, such as Google Maps and Waze. These apps have become very popular for turn-by-turn route guidance that can take account of, and help avoid, traffic congestion and provide estimates of journey time before setting out. These features help tackle the main problem of traffic congestion which is journey time uncertainty.

I would expect that collaboration between public and private sectors would improve both the experience for road users and the efficiency of network operations.

In late July the Government published its Plan for tackling roadside nitrogen dioxide (NO2) concentrations, to reduce these below the statutory limit. Publication was met by considerable criticism that the Plan lacked urgency and effectively dumped the problem on the most affected local authorities, which would be required to implement Clean Air Zones (CAZ).

An accompanying 155-page Technical Report included, on its final page, new estimates of the economic benefits from reducing damage to health through measures to reduce NO2. Remarkably, these new estimates were very substantially below those that had been published in the Technical Report of May 2017  that accompanied the consultation preceding the Plan. For instance, the previous estimated health benefit of a further 21 CAZs was £3.6bn, but now is £620m – an 80% reduction.

This huge reduction was attributed to new advice from the independent experts of the Committee on the Medical Effects of Air Pollution (COMEAP), which had found it difficult to disentangle the impacts of specific pollutants, in this case NO2, from that of the whole mix of traffic related pollutants.

COMEAP’s previous advice recommended a central coefficient of 1.025 per 10ug/m3 NO2, which means that for every 10ug/m3 increase in NO2 concentration, the increase in mortality risk would be 2.5%. The revised advice now recommends a coefficient of 1.023 for traffic-related pollution; but COMEAP also recommends that when measures are primarily targeting NO2 emissions this coefficient should be adjusted to account for possible overlap between the direct impacts of small particulates and NO2. Applying their recommended adjustment, the resulting coefficient used for the analysis is 1.0092.

My enquiries of the Government’s Joint Air Quality Unit elicited the confirmation that overall the updated NO2 damage costs for road transport are approximately 80% lower than those used at consultation. This splits into roughly 60-65% resulting from the revised COMEAP advice and the remaining c.15-20% resulting from the other updates such as new dispersion modelling and population data. The JAQU confirmed that the reduction in the road transport NO2 damage cost primarily reflects a reduction in the estimated mortality impact associated with NO2 alone.

There has been widespread interest and concern about the health impacts of roadside air pollution over the past year and more. So it is surprising to learn of such a substantial downward revisions of official estimates of health impact. However, the relevance for policy is as yet unclear.

Current policy is driven by the need to avoid exceeding statutory limits for NO2 concentration laid down in a EU Directive that applies uniformly to all regions of the Community, in which context the scale of health benefits from remedial measures is not relevant. However, Britain is to leave the EU, which may open the possibility of regulation of air quality based on UK targets set to reflect the balance of benefits in relation to costs. A down rating of health benefits would then be relevant, particularly given the expected reductions in pollutants from improved vehicle technology and from the introduction of electric propulsion. Whether the Government would be willing to propose targets to reflect UK conditions remains to be seen – it may depend on the outcome of the Brexit negotiations and on a judgement about the politics of air pollution.


A version of this post was published in The Conversation on 30 August 2017







Lord Wolfson offered a prize worth £250,00 for the best proposal in response to the question: ‘How can we pay for better, safer, more reliable roads in a way that is fair to road users and good for the economy and the environment’.

The winner was Gergely Raccuja, a recent UCL graduate, now a transport planner with Amey Consulting. His proposal has the merit of simplicity: replace Fuel Duty and Vehicle Excise Duty, receipts from which are declining as vehicles become more fuel-efficient, with a per-mile charge that would depend on a vehicle’s weight (reflecting the damage caused to the road) and emissions (damage to the environment). The charge would be collected by the insurance companies, the new charge being in effect a supplement to the insurance premium.

The impact of congestion caused by a vehicle is captured in a crude way by a distance-related charge. However, the opportunity to relate the charge to the level of congestion was not taken because of the perception that it would be unpopular and hence prevent the new charging scheme being adopted.

Some of the other finalists for the prize proposed schemes involving charging that reflected in part the contribution of vehicle users to congestion, but these were not favoured by the judges.


It is very welcome that a new entrant to the transport planning profession was the prize winner, with a relatively simple proposal. But is it likely to be taken up? My sense is that implementation would not be seen as worth the effort and upheaval. Perhaps the main advantage is that electric vehicles would contribute to the costs of the road system, but for that purpose the proposal might be applied to EVs only, leaving Fuel Duty in place for vehicles with internal combustion engines.

The main shortcoming of the prize-winning proposal is the failure to address the problem of road traffic congestion and how it might be mitigated by charging. Public perceptions are important, of course, but I found it odd that there is no mention of London congestion charging, which has proved quite acceptable.

Any change to how we pay for roads should take the opportunity to ameliorate road traffic congestion, which is the biggest problem of the transport system. Arguably, the question set for the prize was misconceived, with its opening emphasis on ‘How can we pay for….’. It might have been better to ask ‘How can we achieve better, safer, more reliable roads….’


There is considerable interest in, and support for diesel scrappage schemes. The challenge is to target polluting vehicles making the biggest contribution to poor air quality. In my recent blog on air quality, I said that it would be hard to devise a scrappage scheme for the more polluting diesel vehicles. On reflection, I can see a way forward.

The Mayor of London has advocated a national diesel scrappage fund. Transport for London has developed detailed proposals that involve targeting small businesses, charities, schools, low-income households and the oldest taxis, at a total cost for London of some £500m. The recent Defra/DfT Technical Report on reducing NO2 levels considers a national diesel scrappage scheme aimed at all pre-Euro 6 diesel cars and vans, and also a scheme to replace non-compliant vehicles with battery electric vehicles. The former is extremely expensive, while the latter makes very limited impact.

I propose that a scrappage scheme could be integral to the  Ultra Low Emission Zone (ULEZ) proposed for London, which would naturally target the vehicles making the greatest contribution to poor air quality.

The ULEZ will generate net revenue that could be used to fund a scrappage scheme. The targeted vehicles would be those that pay the largest cumulative charges for entry into the zone, since these make the greatest impact on air quality. The formula might be a contribution of £X00 to scrappage for every £1000 of cumulative charges – a cash-back offer. The value of X could be adjusted in the light of experience of uptake.

Owners scrapping a car or van under the scheme would need to provide evidence that the vehicle had been scrapped. To discourage replacement by a further polluting vehicle, it might be a condition of the scrappage scheme that the owner would not be allowed in future to pay the standard charge for entry of a non-compliant vehicle into the ULEZ, and would therefore incur the penalty charge should this be done.

Over time, as non-compliant vehicles are scrapped, revenue from the ULEZ would fall, as would NO2 levels. Depending on how far the latter was from the statutory limit, the scope of the zone could be extended, whether to more recent vehicles or to a wider geographic area.

I suggest that TfL considers in detail how a scrappage scheme might work as part of a the ULEZ, and what incentives might be sought from the Government to adopt such arrangements.

The Government recently published its latest draft Air Quality Plan for reducing nitrogen dioxide (NO2) in towns and cities. This followed loss of a court case in which the previous Plan was found wanting, particularly by not fully recognising the poor on-the-road emission performance of diesel cars, despite their seeming compliance with regulatory requirements in laboratory tests. This latest Plan has been criticised as inadequate by many protagonists and press commentators.

Nevertheless, the new draft Plan and accompanying Technical Report represent a significant advance analytically, being based on systematic review of options, assessed using multi-criteria analysis and cost-benefit analysis. Impacts include health benefits, social and government costs, time savings from improved traffic flow, and change in greenhouse gas emissions.

The starting point is that road transport is by far the largest contributor to NO2 pollution in the 40 local authorities in England where the statutory limit values are exceeded. London has much the highest level – mean annual concentration in excess of 100 μg/m3, compared with the statutory limit of 40 μg/m3.

The most cost-effective – indeed the only worthwhile – approach to mitigation is through establishing Clean Air Zones (CAZs) where targeted action is taken. The 2015 Plan proposed CAZs in London and 5 other cities. This 2017 Plan extends coverage to 27 in all, reflecting updated assumptions about diesel emissions.

A key issue is whether a CAZ should require that the more polluting vehicles be charged for entry. For locations where NO2 levels are only modestly in excess of the legal limit, measures other than charging may suffice. Nevertheless, the Technical Report models the impact of charging in all 27 cities, which would involve set-up costs of £270m. For 12 of these, charging could be limited to public service and goods vehicles, but for 15 it would need to extend to cars not compliant with the latest Euro 6 diesel standard. The main impact of charging is assumed to be a two-thirds reduction of trips by non-compliant cars. A charging CAZ is projected to result in an 18% reduction in NO2 levels in the first year of impact.

A variety of other measures to reduce NO2 levels are considered in the Report. One approach that has attracted much support is for a scheme to offer payments to owners to scrap older polluting vehicles. The Report states that a national scheme to scrap all pre-Euro 6 diesel cars and vans could cost £60 billion. A scheme limited to replacement by battery electric vehicles assumes that only 15,000 vehicles would be scrapped.

The Report does not consider targeting by area, for which London would have a strong case for funding given the high NO2 levels, although this would be politically contentious. High mileage polluting vehicles would be the target. However, the difficulty is that the oldest vehicles tend to be both most polluting per distance travelled but least used, and owned by low-income households for whom the cash incentive would need to be high. So a well-targeted scrappage scheme seems hard to devise.

Transport for London is consulting on an Ultra Low Emission Zone (ULEZ) – effectively a charging CAZ – to cover the same area as the Congestion Charge. Non-compliant cars and vans will be charged £12.50 a day, which will apply 24/7 from April 2019. This is in addition to an emissions surcharge on top of the congestion charge for pre-Euro 4 cars and vans of £10 from October 2017. There is also a London-wide Low Emissions Zone in operation since 2008 that charges polluting heavy diesel vehicles.

On introduction, the ULEZ is projected to reduce the proportion of road kilometres exceeding limit NO2 values in Central London from 82% to 70% – a moderate air quality benefit but far from sufficient. This suggests that the charge and/or scope may need to be increased in future.

Introducing the ULEZ is relatively easy in London, given the existing of the Congestion Charge arrangements for payment and enforcement. Other cities needing to adopt a charging CAZ could adopt the technology used by London, in which case it would be natural to use it for congestion charging, both to manage peak demand and to raise revenue for investment in local transport. If 27 cities have such arrangements, this constitutes the nucleus of a national road user charging framework, which could be used to raise revenue for the road system as electric vehicles gradually take over, given that these do not pay fuel duty. The Government’s ambition is for all new cars and vans to be zero emission by 2040, and for nearly every car and van to be zero emission by 2050.

Seeing charging CAZs as a precursor to general road pricing would be contentious. This may be why the Government wished to delay publishing its draft Air Quality Plan until after the election, and why in the published consultation document the Government has been coy about charging, stating: ‘The Government believes that charging zones should only be used where local authorities fail to identify equally effective alternatives.’ The analysis presented suggests that the alternatives are unlikely to be sufficient.

The present objective is to reduce NO2 emissions to below the statutory limits specified in the EU air quality directive. However, Britain is to leave the EU, which may open other possible approaches, for instance setting policy targets expected to be achievable with available technologies and resources, balancing benefits against costs. In the long run, the problem of transport NO2 emissions will be solved by switching to electric vehicles – which arguably should be the policy priority.

This blog is the basis for a Viewpoint article in Local Transport Today of 26 May 2017.










The current main method of adding capacity to UK motorways is known as Smart Motorway All Lane Running. This involves allowing traffic to use the hard shoulder (previously reserved for breakdowns), with speed controls to respond to accidents and congested conditions. This approach has been applied to a section of the M25, London’s orbital motorway, increasing running lanes from 3 to 4. A monitoring report after two years of operation has been published. The main findings, compared with before the scheme was introduced: traffic flows up by as much as 17%, well above the regional trend (5%); some journey times increased by up to 8%; and only a slight improvement in reliability. Significantly, the biggest increases in traffic occurred at weekends (as much as 26%).


The intention of investment to increase the capacity of the Strategic Road Network, of which the M25 forms an important part, is to improve connectivity between cities and reduce congestion. However, roads like the M25, that are located in densely populated areas, are also used by local users for their daily travel. Any increase in capacity offers opportunities for more or longer local trips.The resulting extra traffic restore congestion to that it had been prior the the investment in capacity. The findings of the present study are consistent with this general experience. Regrettably, there is no data on the composition of the traffic, by journey purpose or distance travelled. However, the finding of a big increase in weekend traffic is consistent with leisure users taking advantage of initially faster travel to reach more distant destinations.

The findings of this report confirm the phenomenon of ‘induced traffic’ – the traffic that results from additional road capacity – as I discussed recently in connection with the CPRE study. Such traffic adds to congestion and so reduces the time savings expected from such investment, time savings that constitute the main economic benefits presumed to justify the investment.


Bruce Schaller, an expert on urban transportation, has published an informative and insightful report on the impact in New York City of what he calls ‘Transportation Network Companies’ (TNCs) such as Uber and Lyft. Use of these providers of app-based ride services has grown rapidly, more than doubling in each of the past four years. This reflects the popularity of the services offered, which reduce anxiety, uncertainty and stress, not least by providing assurance of a vehicle in situations where hailing the traditional yellow cab may be problematic.

The contribution of the TNCs to congestion has been a matter of controversy. The present report confirms a previous study carried out by the NYC authorities which found that worsening congestion was driven primarily by increased freight movement, construction activity, pedestrian volumes and record levels of tourism, all of which put growing demands on the streets’ limited capacity. However, use of TNCs continue to grow, raising the question of their future impact on congestion.

A key question is whether TNC growth is making more efficient use of scarce street space by putting more passengers in each vehicle, as with UberPool which offers low fares for trips shared with others? Or does it add to traffic by diverting people from high capacity services such as rail and bus, for which evidence of a recent decline in ridership is suggestive? The available evidence as a whole is insufficient for a definitive answer, but the report suggests that diversion is likely to be more important, implying  that TNC’s add to congestion.

The report is concerned that TNCs are fundamentally undoing the cost incentives to use public transport. NYC taxi fares were traditionally set at about 4.5 times the subway fare to encourage the use of transit (public transport). However, as they cut fares, the TNCs are beginning the erase these disincentives to road vehicle use. These fares do not reflect the costs of time delays arising from congestion, hence there would be a case for some kind of congestion charging.


Congestion is self-limiting in that as traffic builds up, for instance from more TNC vehicles, speeds drop, trips take longer, and some road users make alternative decisions, for instance to travel at a less busy time, or to go to a different destination, or to use the subway. So it is not to be expected that growth of TNCs would worsen congestion in already congested parts of NYC. The switch of people from the subway to TNC services would be limited for the same reason.


My new book, Travel Fast or Smart?, is one in a series of short books on policy and economics topics described as ‘essays on big ideas by leading writers’. My contribution is a critique of the inconsistencies of transport policy in recent decades, which I attribute to the shortcomings of conventional transport economic appraisal in identifying the benefits that arise from investment.  This book is available both in print and as an ebook from Amazon Books

There is much current interest worldwide in the concept of Mobility-as-a-Service (MaaS), the aim of which is to provide seamless journeys using the most appropriate travel modes, routed and ticketed by means of a smart phone app. The MaaS provider ‘aggregates’ the services provided by transport operators (in the way that Amazon acts for retail product providers). MaaS is intended to be an attractive alternative to private car ownership. The Transport Catapult has recently published a report on the opportunities for MaaS in the UK. And the New Cities Foundation has addressed the role of public transport operators in its development.

There are many recognised technical and policy issues that need to be tackled, including managing the large amounts of data, and coordinating ticketing and payments on behalf of a multiplicity of operarors. However, there are two aspects that deserve particular consideration. The first is the ability of MaaS to cope with peak travel demand.

Peak demand

Daily travel demand is characterised by morning and evening peaks, and there are also seasonal variations. Peaks result in road congestion and crowding on railways. One approach would be to charge higher prices at times of greatest demand, with the aim of spreading the peak. This model has been adopted in the aviation sector, led by the low-cost carriers, and by Uber for urban taxis (and also in other sectors such as hotels). The railways offer off-peak discounted fares, but do not flex fares upwards to reflect actual peak demand.

However, unless peak pricing is part of the public transport provision (which at present it is not), the scope for coping with peak demand for multi-modal journeys is quite limited. This means that unreliability of travel time for each stage of a journey would present a scheduling problem.

While MaaS comprises a minority of all trips, congestion would be a given, and scheduling would need to allow for expected journey stage times plus a margin for uncertainty, with rerouting in the event of unexpected congestion. On railways, consideration would need to be given to offering alternatives to overcrowded trains. Such dynamic scheduling could be technologically challenging.

Were MaaS to grow to encompass a substantial part of travel demand, there may be scope for routing travellers to spread demand across the network in a way that optimises overall efficiency, simplest for routes that involve stages with assured reliability – rail, bus rapid transit, walking and cycling. There would also be scope to consolidate car trips by means of shared taxis, as with UberPOOL. However, such sharing, incentivised by lower fares, could attract passenger from buses, which could add to congestion.

If MaaS were to be a major intermediary in meeting travel demand, a significant operational issue would be whether to respond to peak demand for door-to-door travel by mobilising more taxis through surge pricing, as does Uber. Surge pricing to deter demand and increase supply is sensible in the absence of congestion, but may not be optimal under congested conditions. In the absence of surge pricing, demand would exceed supply and would be rationed by waiting in a virtual queue until a taxi becomes available. With surge pricing, there is a greater supply of taxis and so less waiting time, but journey times might be slower on account of increased congestion. Which approach would be optimal would require modelling.

Surge pricing works well for aviation, a closed system where an aircraft can only fly if it has airport slots allocated at trip origin and destination. But roads are an open system and hence prone to congestion at peak times in populated areas. MaaS would be more straightforward to implement in lower density areas, less so in urban centres, unless private cars were entirely replaced by a fleet of shared use self-driving vehicles, as has been suggested.

Who owns the platform?

The question of how MaaS can best cope with peak demand is linked to the second problem – the nature of the platform by means of which demand and supply are matched, prices set and revenues allocated. The central issue is familiar: benefits of competitive supply versus benefits of an integrated network. Experience is varied. In the case of buses, Mrs Thatcher’s government opened the bus services outside London to competition with minimal regulation, hoping to benefit users by on-the-road competition between private sector operators. This largely failed to materialise since such competition resulted in unattractive profit margins. In consequence, the present Government has introduced legislation that would allow other cities to adopt the successful London model, whereby an integrated public transport network is operated by a politically controlled public body, Transport for London.

For MaaS, the question is whether an open source public platform would naturally evolve on account of the superior benefits, as envisaged by the TravelSpirit collaboration. Or whether competition in the market between competing platforms would be the main driver, with perhaps a dominant platform emerging through economies of scale and scope.

A dominant private sector platform might need to be regulated to avoid market failure that allowed economic rents to be extracted at the expense of users. The MaaS provider would have access to all the data arising from use of the system. Fair sharing of this data with transport providers would help meet the needs of users. On the other hand, discriminatory sharing could increase returns to the provider.


Traffic congestion is the main problem of the road system. A key question is whether MaaS has the potential to lessen traffic congestion. If it does, then promoting MaaS could be a sensible transport policy, in which case a view would need to be taken of the relative attractions of competing platforms versus a single public platform.

In the longer run, developments in shared use driverless urban vehicles might achieve substantial mitigation of urban traffic congestion. Sharing of taxis would increase vehicle occupancy and hence efficiency of the road system; demand management could limit use of single occupancy vehicles under congested conditions; and the development of vehicle-to-infrastructure communications could permit flow management, analogous to air traffic control. In such circumstances, MaaS would be likely to be an integral part of an urban transport management system. However, development of such a system would be challenging in respect of technology, business models, institutions and public acceptability – hence the feasibility and timing is uncertain. In the meantime, development of MaaS in urban areas would need to cope with traffic congestion.