London has had a road user charge since 2003 – a charge for entering a central zone during working hours, known as the ‘congestion charge’. This has proved workable, publicly acceptable and generates useful revenue, although the impact on congestion was fairly short term, as I explained previously. However, the fixed daily charge for entry means that the cost to drivers is unrelated to distance travelled or to traffic levels.The congestion charge is now supplemented by a charge on older polluting vehicles, which will be extended beyond the present central zone to cover much of London in 2021.

A study of more sophisticated alternatives has recently been published by the Centre for London. The proposal is to charge per mile in areas of high demand and poor air quality. Rates would vary by vehicle class and emissions, local levels of congestion and air pollution, and the availability of public transport. The charging system would be linked to individuals, not to the vehicle as at present, and would be based on a smartphone app that offered journey options alternative to the private car. An attractive feature is a refund if a trip takes significantly longer than estimated.

Modelling of the impact of the proposed charging scheme was undertaken although not published. There is some ambiguity in the reported findings (p61 of the published report). On the one hand it is stated that ‘for the average driver making a 10 km journey, we expect this [the charge] to amount to in the region of £1.50 – the cost of a cup of coffee or a bus ticket – although journeys in the most congested and central parts of the city, using the most polluting vehicles, would be charged much more.’ But is it also stated that ‘Charging drivers on the most congested roads the equivalent of a cup of coffee or a bus ticket could reduce emissions and air pollution by up the a fifth.’ So not clear whether the charge on the most congested roads is about £1.50 or much more.

The problem with road user charging in a city like London, with many relatively high income and business drivers, is that a charge of £1.50 for a 10 km trip is likely to be far too little to have a significant impact on congestion. Charges that would make a useful impact would be tricky politically. A proposal to introduce a whole new technology for charging would prompt anxieties about higher charges.

In my view, the best approach would be to increase the present charge of £11.50 per day to something like £15, and then to offer a discount to say £10 if paid via a smartphone app. Once such a new payment method is established, there would be scope for varying the charge to reflect congestion levels (which should be acceptable if the charge were always less that the standard daily charge). This approach would be similar to the introduction of Oyster and contactless card payments in London, with daily caps on charges.

 

Smart Motorways, a flagship programme of Highways England, aims to relieve congestion by converting the hard shoulder into a running lane and by varying the speed limit to smooth traffic flow. To assess performance in practice, Highways England has been monitoring closely the section of the M25 between Junctions 23 and 27 since the widened road opened in 2014. Three annual reports have been published, detailing traffic flows, journey times and safety, and comparing outcomes ‘before’ construction and ‘after’ scheme opening. Traffic growth of 16% was observed at Year 3 compared with before opening, far higher than regional motorway growth over the same period, with increases in weekend traffic of up to 23%.

Such traffic growth seems a noteworthy example of induced traffic, the traffic that arises as a result of increased capacity and which tends to restore congestion to what it had been previously. I therefore made a Freedom of Information request to see the traffic forecasts and economic appraisal that were the basis of the investment decision.

The traffic forecasting report was based on a variable-demand multi-modal model for the M25 area, employing the SATURN suite of programmes, updated to take account of the most recent national datasets for trip ends and similar. Traffic forecasts were made for the assumed 2015 scheme opening year, the 2030 design year and the 2040 horizon year, for the morning and evening peak flows and the interpeak period, comparing the ‘do-minimum’ case, without the investment, and the ‘do-something’ case with it.

The time slices used for the forecast and the outturn monitoring are regrettably different, which limits comparisons at particular times of day. Comparisons may, however, be made of average daily traffic flows (ADT). For the section J23-24 clockwise, for instance, the forecast ADT increase, comparing the scheme with do minimum, was 13% in 2015 and 16% in 2030. The outturn monitoring found an increase of 13% at Year 3 after opening compared with before, in good agreement with forecast.

The economic appraisal report employs the DfT’s TUBA software to derive estimates of monetarised travel time savings and vehicle operating costs (VOC) from the traffic forecasts, comparing do-something and do-minimum cases. The main economic benefit is travel time savings to business users, worth £475m, because the scheme was expected to allow travel at higher average speeds than the do-minimum case. Time savings to non-business travellers (commuters and others) were very largely offset by increased VOC, given the assumed diversion from local roads onto the motorway generating longer trips. As an example of the origin of the time savings, the speed on J23-24 clockwise for the AM peak in 2015 was forecast to be 86 km/hr with the scheme, versus 76 km/hr without. The overall benefit to cost ratio (BCR) was 2.3, later adjusted upwards to 2.9.

However, this forecast increase in speed failed to materialise. There has been effectively no change on average for all days and time slices between before opening and Year 3 for the clockwise travel. For anticlockwise, an average saving of 15 seconds (1.4 per cent) was found for a journey of 16.6 min before the improvement. Time savings of 6% and 9% respectively were seen at Year 1 after opening, but were lost by Year 2.

Generally, traffic flowed at the free flow rate except during the PM peak when it was slower. Surprisingly, the extra lane did not permit a faster flow at this PM peak, even though the increase in capacity of 33% was greater than the increase in traffic volume. Possibly the use of variable speed limits to smooth the flow was at the cost of journey time savings.

The stated conclusion of the Year 3 monitoring report is that ‘increases in capacity have been achieved, moving more goods, people and services, while maintaining journey time at pre-scheme levels and slightly improving reliability.’ Yet this conclusion undermines the economic case for the scheme, based on forecast time savings. This in turn raises questions about both the validity of the modelling and of the orthodox approach to appraisal.

We know from the National Travel Survey that average travel time has remained essentially unchanged for at least the past 45 years. This implies that any travel time savings must be short run. In the long run, people take advantage of transport investments that permit faster travel to gain access to more distant destinations, services, opportunities and choices, within the limited time they allow themselves for travel. This change in travel patterns would first be seen in optional trips, consistent with the big increase in weekend traffic in the M25 example, and subsequently over the years as people move home and change jobs. The consequential additional traffic – induced traffic – adds to congestion and negates the time savings that are conventionally supposed to be the main economic benefit.

If we are to make transport investments that are good value for money, we need to pay attention to the real-world consequences, and not be misled by the outputs of models that generate the notional time savings to which transport economists are so attached. We need to constrain models to hold average travel time constant in the long run, consistent with the findings of the National Travel Survey. To calibrate models, we need data on origins, destinations and purposes of trips, and how these change when a road is widened. And we need to work out how to value access benefits to users.

 

This blog is based on an article published in Local Transport Today 24 May 2019

 

 

 

 

I recently participated in a conference on the Future of the Car, organised by the Financial Times, which prompted the following thoughts.

The car industry is in a state of flux as it engages with four new transport technologies. Electric vehicles will eliminate both carbon and noxious tailpipe emissions, and go a long way to achieving sustainable surface transport. Autonomous vehicles are expected to work wonders, but timing and impact in big cities is quite unclear. Digital navigation, now in general use, can optimise routing through congested traffic and provide estimated journey times, so reducing the uncertainty that is the most bothering aspect of congestion. Digital platforms, exemplified by Uber, more efficiently match demand to supply, and also facilitate sharing of journeys.

Vehicle sharing is seen by many as the answer to road traffic congestion. Certainly, if the numbers of trips were fixed, increased vehicle occupancy would mean fewer vehicles and less traffic. But trip numbers are not fixed. Congestion arises in areas of high population density and high car ownership. The capacity of the road network is insufficient to accommodate all the car trips that might be made. Some are supressed by the prospect of unacceptable time delays as car owners made other choices – of mode or time of travel, of destination where there are options (as for shopping), or not to travel at all (ordering goods online, for instance, or working at home). Interventions intended to reduce congestion, such as vehicle sharing, initially free up road space and reduce delays, but this attracts previously suppressed trips, restoring congestion to what it had been. This is also the basis for the maxim that you can’t build your way out of congestion, which we know from experience to be generally true.

The most important transport innovations of the past had a crucial characteristic. They achieved a step-change in the speed of travel, allowing us increased access to desired destinations, opportunities and choices, as we saw with the railways, the car, commercial aircraft, the bicycle in its heyday, and motorised two-wheelers today in low income countries. Step-changes in virtual access to services and people have been achieved by a succession of electronic innovations – the telegraph, telephone, radio, television, internet, broadband, mobile phone, social media. All these innovations have been transformative and have rewarded the huge investments that made them possible.

In contrast, the new transport innovations do not permit a step-change in the speed of travel. They will not increase our access and will not be transformative. The car of the future will be electrically propelled, will have extensive digital functionality as well as self-driving options. But the car of the future will not progress faster through urban traffic than the car of today.

What the new technologies offer are incremental improvements to the quality of the journey. Users will take up such options if they are perceived to offer value for money. The auto industry will need to drive down the costs of the innovative features, which of course is what the industry has always strived to do. The future of the car, and of the industry, will be more like the past than many seem to suppose.

A version of this blog appeared in the FT’s Alphaville blog.

 

 

I blogged recently about the review of the law governing autonomous vehicles (AVs) that is being carried out by the British Law Commission. One aspect not considered in the consultation document is the implications for vehicle connectivity. I have submitted a response to the consultation to make the following points.

Adaptive Cruise Control, available in some current production vehicles, adjusts the gap to the vehicle in front using sensor data to vary speed. Connected (or Cooperative) Adaptive Cruise Control (CACC), an emerging technology, takes data from vehicles further ahead using vehicle-to-vehicle (V2V) communications, which allows shorter headways and attenuates traffic disturbance to achieve smoother flow. The shorter the headway, the less scope for driver control. In the limit, CACC allows platooning of vehicles on inter-urban roads – ‘road trains’ involving vehicles in close proximity with a lead driver in control. The postulated benefits of platooning include better fuel economy and decreased emissions resulting from lower aerodynamic drag, improved traffic flow and capacity, and lower labour costs. A number of truck manufacturers have initiated trials and more are planned. The 2016 European Truck Platooning Challenge involved six manufacturers sending platoons from starting points in five different countries to end at Rotterdam, gaining valuable practical experience.

Much of the past impetus for the development of connected vehicles came from research funding provided by the US Department of Transportation. The main motive was to improve safety through vehicles exchanging data about speed and location, and vehicles acquiring data from roadside infrastructure about road conditions. There are two competing telecoms technologies under consideration: short-range WiFi for V2V being developed by the car manufacturers for platooning; and a system based on the next generation 5G mobile phone technology, to be installed in both vehicles and infrastructure, and able to signal at longer range.

Unlike truck drivers, the generality of drivers of AVs would be able to choose the gap to the vehicle in front. It is not clear why, without an incentive, they would choose a gap smaller than that with which they are comfortable, which may not be very different from current headways. Accordingly, to increase road capacity by reducing headway there would need to be some incentive that would impact on individual drivers. This might be a road user charging regime that charged on the basis of the length of carriageway effectively occupied.  Another kind of incentive to reduce headway would be dedicated lanes that are less congested and faster flowing than other lanes, analogous to High Occupancy Vehicle lanes on US highways. Acceptable incentives would be needed if manufacturers were to go beyond equipping vehicles with the existing Adaptive Cruise Control. If manufacturers are to be held be responsible for the safe functioning of AVs, adding V2V or vehicle-to-infrastructure connectivity (V2I) to reduce headway would exacerbate this responsibility by introducing functionality that depends on that of other manufacturers and suppliers, and that increases the risk of security breaches.

More generally, connected vehicles operating at short headways would require reconsideration of the safety regime concerned with the crashworthiness of individual vehicles. A system of connected vehicles would require consideration of fault modes at system level, for instance the consequences of faults in individual vehicles in a platoon or faults in connectivity, including faults from hostile interventions. It would not be surprising if there were trade-offs between headway and safety that limited possible increases in effective road capacity.

The current industry-wide technological thrust is directed towards vehicle autonomy, not connectedness. The logic is that the general application of V2V connectivity would need to follow on from the successful adoption of vehicle autonomy – because the benefits of such connectivity largely depend on response times of connected vehicles that are faster than achievable by human drivers. There would then be a question of whether access to certain classes of roads should be limited to vehicles equipped with V2V technology. However, the efficiency gains from such dedicated infrastructure use would depend on widespread adoption of V2V communications, for which, as noted, there may be a lack of incentive for vehicle manufacturers to develop.

Although the potential of connectedness is unclear at present, it would be sensible for a new legal regime to allow for this possibility. On the railway, statutory regulations place a duty on infrastructure managers and operators to develop safety management systems, as well as a duty on operators to work together to ensure safety. However, the railway is a closed system that can be used only by authorised operators, whereas roads are generally open to all qualified users.

One approach would be to regard V2V and V2I connectivity as simply extensions of visual detection of other vehicles and roadside signs and signals. From this perspective, the legal framework for AVs may not need to be modified to deal with connected vehicles. On the other hand, it is arguable that the absence of some kind of system-level safety requirement would be incompatible with public expectations in the event of a crash involving numbers of connected AVs.

The advent of autonomous vehicles (AVs) will require reform of the road traffic legislation and the law dealing with the safety of road vehicles. The Law Commission, the body responsible for reviewing law in Britain, was asked by the government to review the legal framework for AVs. It has published a 230-page consultation, a very impressive analysis of the technological possibilities and their implications – a good example of what you can get when industrious lawyers get to work on a meaty topic. The summary is a handy introduction to the issues.

One innovative concept tentatively suggested is that of the ‘user-in-charge’, to cover situations where a human may be called on to take charge of an AV in certain circumstances. The user-in-charge would be a person who is qualified and fit to drive, unless the vehicle is specifically authorised as able to operate without one. So any vehicle at Level 4 and below would need such a person to be available, who would not be the driver when the automated system is functioning. For example, a driver might take the car to the motorway, and then engage automated mode, during which time they could undertake some other activity. They would need to be available, as user-in-charge, to take over if automation were to be no longer possible in the event of some malfunction, as well as to drive off the motorway.

 

 

An interesting report, from a new organisation called Transport for New Homes, examines a number of greenfield housing developments in Britain, criticising most of them for generating excessive car dependence. This is in part due to location away from existing centres, and in part to disregard of public transport possibilities in the planning process. Generally, the arguments are well made. However, what is missing is survey evidence of the experiences and attitudes of occupants of these new houses. The BBC reports a couple of anecdotal examples of dissatisfaction of residents. Yet these may not be typical since those whose choose to live in such housing may prefer the car to the public transport, walking and cycling alternatives. After all, car dependent lifestyles are adopted by choice by many residents of cities where alternatives exist.

The developers of new greenfield housing construct new properties to sell, which they of course do, reflecting the need for new housing and the preferences of many for location away from traditional urban centres. The lack of public transport provision tends to arise from the relatively small scale of developments, in a context in which bus use is generally on the decline. The report discusses some developments of new urban quarters in the Netherlands, where the scale and location adjacent to existing towns means that good public transport provision is feasible. One example, Almere, is a planned city built on land reclaimed from the sea, which makes large scale development possible. In Britain, assembling land on that scale has not been attempted since the post-War new towns.

It would be worth considering innovative approaches to transport provision for greenfield housing developments, for instance as in Pinellas County, Florida, where residents can use a subsidised Uber service to reach the core bus routes – known as ‘micro-transit’.

An independent Commission on Travel Demand, funded by UK Research Councils, recently issued its report, based on evidence and expert advice. There is no single message, other than that there are more uncertain factors influencing travel demand than conventionally supposed. However, the report make ten sensible recommendations for better processes.

I was disappointed that the report did not consider two matters on which I had submitted evidence. One is that demand for any kind of product or service may saturate, that is, cease to grow once all needs are met. For instance, ownership of many household goods, such as washing machines, exceeds 90%, so that demand no longer reflects growing tes, but only replacement plus population growth. There is evidence consistent with saturation of demand for daily travel for many purposes. For instance, 80% of the urban population of Britain have a choice of three or more large supermarkets within 15 drive minutes of home, and 60% have a choice of four or more. If you have a choice of 3-4 supermarkets within 15 minutes drive, you may not be inclined to drive further to have a choice of a fourth or fifth, in which case your demand for travel to supermarkets is said to have saturated.

Second, given that average travel time has not changed for at least the last 45 years, as measured in the National Travel Survey, increased travel demand (distance per capita) must require faster travel. This is now hard to achieve, given high levels of car ownership and the limited scope for this to grow, plus a mature road network where congestion proves difficult to mitigate. We have High Speed Rail on the way, but rail is a minority of all trips, so HSR would be a minority of a minority, with little impact on average speed.

The travel time constraint, coupled with the speed constraint, means that travel demand per capita is unlikely to grow significantly in the future. Total travel demand will be driven by population growth, of course, although the pattern of demand will depend on where the additional inhabitants are housed: greenfield means more cars, urban at higher density implies investment in public transport.

Professor Peter Jones, my UCL colleague, has been leading an EU funded project concerned with urban mobility, past and future, in five Western European cities – Berlin, Copenhagen, London, Paris and Vienna. The report is now available, as is a short speech by Peter.

A trajectory is identified in which cities start by attempting to accommodate the car, see the difficulties in high density locations and so reallocate road space to walking, cycling and public transport, and subsequently move on to focus on place – the role of streets as public realm for non-mobility activities. The figure above shows how car use peaked and then declined in consequence.

Recognition of place as an important quality of urban streets presents a problem for conventional transport investment appraisal, which only recognises the economic benefits of increased mobility. The report advocates ‘vision and validate’ as an approach, as opposed to the traditional ‘predict and provide’, using cost-effectiveness analysis to justify investment to attain the desired balance between mobility and place.

This report is a valuable synthesis of a considerable amount of data and analysis highly relevant to how we think about the future of cities.

 

I have a new article that reviews the evidence for the success of congestion charging (aka road pricing, road user charging) in the three major cities in which it has been tried. In London, there was a marked reduction in both car traffic and delays when charging was introduced, but delays reverted to previous levels by year five. In Stockholm, a similar initial impact was seen, but there was no monitoring of delays subsequently.

Singapore has been successful in using electronic road pricing to maintain desired traffic speeds, adjusting charges up or down according to whether speeds have exceeded or fallen below targets. However, this is only possible because there is a very high charge for vehicle ownership, which has limited this to 100 cars per 1000 population, compared with 450 in the UK and similar or higher figures for other developed economies.

Road traffic congestion occurs in areas of high population density and high car ownership. There are more trips that could be made by car than are in fact made. Some people are deterred by the prospect of time delays and make other choices: a different time or mode of travel, or a different destination, or not to travel at all. Measures that deter some drivers, such as congestion charging, reduce delays when introduced, which makes car travel more attractive to those who are more time-sensitive but less cost-sensitive, so that traffic increases and delays revert to previous levels. Accordingly, congestion is both self-regulating and difficult to reduce.

Although economists believe that road pricing is the proper way to tackle congestion, in practice the level of charges to make a useful impact would probably be too high to be publicly acceptable.