Considerable observational evidence indicates that travel time, averaged across a population, is stable at about an hour a day. This implies both an upper and a lower bound to time that can be expended on travel. The upper bound explains the self-limiting nature of road traffic congestion, as well as the difficulty experienced in attempting mitigation: the prospect of delays deters some road users, who are attracted back following interventions aimed at relieving congestion. The lower bound implies that time savings cannot be the main economic benefit of transport investment, which means that conventional transport economic appraisal is misleading. In reality, the main benefit for users is increased access to desired destinations, made possible by faster travel, which is the origin of induced traffic. Access is subject to saturation, consistent with evidence of travel demand saturation. However, access is difficult to monetise for inclusion in cost-benefit analysis. Consequential uplift in real estate values may be a more practical way of estimating access benefits, which is relevant to the possibility of capturing part of such uplift to help fund transport investment that enhances such access.
The Department for Transport has initiated an exercise to assess how the transport system could be decarbonised, in line with the Government’s commitment to a net zero carbon target for the whole economy by 2050.
I have submitted some thoughts on behavioural aspects, including the scope for increasing active travel, decreasing motorised road travel and air travel, and the need to improve modelling to accomodate such behavioural changes.
The Secretary of State for Transport has announced £2 billion of investment to boost cycling and walking in response to the Covid pandemic. The Mayor of London has plans that he hopes will increase cycling ten-fold and walking five-fold post-lockdown. These intentions take advantage of current public health constraints on use of public transport and are certainly praiseworthy, but there are serious questions about feasibility.
Increasing cycling in London ten-fold would take its share of trips to that found in Copenhagen, where there are segregated cycling lanes on all roads with significant traffic. Moreover, the city is relatively small, such that you can cycle from the centre to the edge in an hour or so, as I have done but would not attempt in London. However, car use in Copenhagen is only slightly less than in London, while public transport mode share is half that in London. This indicates that you can get people off buses onto bikes, which are cheaper, healthier, better environmentally, and no slower in traffic than public transport. But it seems more difficult to get people out of their cars, even in a city where virtually all motorists have current or past experience of cycling. And a decrease in users of public transport, while helpful while the pandemic lasts, would lead in the longer term to loss of fare revenue and of level of service.
Transport for London (TfL) analysed cycling potential in 2017, considering which trips by motorised modes could reasonably be cycled, mainly taking into account trip length. If achieved in full, cycling would be responsible for 40% of all trips, which would be consistent with the Mayor’s ambition. However, a large proportion of potential cycling trips are currently done with at least one other person, which would limit switching. Beyond that observation, considerations of behaviour change and public acceptability were not taken into account.
Boosting walking five-fold is even more problematic, to say the least, given that its mode share of trips in London has long been stable at 25%. Some modest increase in the near term is likely as people avoid short bus journeys. Perhaps the Mayor has in mind to increase the distance walked per trip, which again is likely to some extent in the near term. Yet walking is the slowest mode of travel and time available for travelling is always a constraint. A TfL analysis of walking potential in 2017 estimated that there are more than two million potentially walking trips in London per day, compared with just under one million at present, but most potential walking trips could also be cycled. So it is very hard to see how a five-fold increase in walking could be achieved, even before we consider behavioural factors, in particular the reasons why so many people prefer to drive rather than walk short journeys.
To see if the Mayor’s ambition is realistic, we need a full analysis from TfL, taking into account behavioural aspects, including travel time constraints, and avoiding double counting. It also needs to show that the cost of new cycling infrastructure to meet objectives is affordable, given the current loss of revenue, and to recognise the implications for public transport of the longer-term loss of fare income.
This blog post also appeared as a letter in Local Transport Today 29 May 2020.
The Covid-19 epidemic has prompted discussion of the implications for travel behaviour once it is over. Will the recent downward trend in trips to work and for shopping accentuate? Might people prefer their cars and bikes to travel on crowded public transport? Will there be a bounce back in leisure air travel? All is speculation at present.
More immediately, we see that the new highly infectious virus has prompted huge and rapid global efforts of technological development: tests for the virus and antibody, and novel vaccines. The epidemic has also stimulated extensive efforts to model the consequences, modelling that is open, transparent and collaborative, and that has proved crucial in informing government decisions, in particular to see how new technologies can lessen the need for social distancing.
There are lessons for the transport sector, for which the main priority must be decarbonisation to achieve the government’s net zero carbon target by 2050. Technological development should be stepped up in the areas of batteries for surface transport, and new propulsion technologies for aviation and marine. Electric charging infrastructure needs to be made generally available to stimulate the purchase of electric vehicles.
The models employed in the transport sector are neither open nor transparent. They are obsolete in that they were developed well before current concerns with carbon emissions and are deficient in predicting observed outcomes. We need a new generation of travel/transport models that are open, transparent, and possibly crowdsourced, to inform decisions on policies for decarbonisation, including how new technology can complement behavioural change.
Transport decarbonisation is the top priority. In contrast, automation is not important. As I argued in my recent book, Driving Change, autonomous vehicles will be difficult to deploy on the existing road network, and the benefits are quite limited. It is for the car industry to develop automated features if it thinks that customers might purchase such vehicles. It is for governments to put in place suitable regulatory regimes. But it should not be a priority for governments to support the development of the technology, which would be a distraction from decarbonisation efforts.
This blog post appeared also as a letter in Local Transport Today 17 April 2020
The Department for Transport’s (DfT) second Road Investment Strategy (RIS2) was published at the time of the recent Budget, committing to spend £27.4bn over the next five years on the strategic road network (SRN). The stated main priority is to maintain the existing roads. Only where existing roads are ‘simply not up to the job’ is the Government asking Highways England to develop wider, realigned or, in a few cases, wholly new roads to keep people and goods moving. Yet expenditure on maintenance is expected to be £12bn, whereas capital enhancements are worth £14bn.
Prioritising investment is based on the 2018 Road Traffic Forecasts, projecting growth on the SRN in the range of 29% to 59% by 2050. This suites the civil engineers of Highways England who see their main purpose as building roads. However, as I have argued previously, the DfT traffic forecasts are very problematic and have generally proved to overestimate outturn traffic levels. Moreover, as I noted in chapter 2 of my recent book, the rate of addition of lane-km to the SRN in recent years has been less than the rate of population growth, despite the high levels of spend.
It is therefore not surprising that average delays on the SRN have worsened during the RIS1 period, growing from 8.9 seconds per vehicle mile to 9.5 seconds per vehicle mile. The DfT’s ambition for performance at the end of RP2 is to be no worse than at the end of RP1. This is a very modest aspiration, and contrasts with the aim of the previous road investment strategy (RIS1) of a free-flow core network with mile a minute speeds increasingly typical.
The new ambition is consistent with the document’s recognition that it is ‘widely accepted that it is not possible to outbuild congestion across the whole of the road network’. Accordingly, investment is to be focused on congestion hotspots, so that average network performance will be at least as good in 2025 as it is in 2020. Yet, as I have pointed out, adding capacity induces more traffic, so tackling congestion hotspots has little impact beyond perhaps shifting congestion to another part of the network.
One odd feature of this and similar publications of Highways England, is the disregard of digital route guidance (Google Maps, Waze and others) that is in very wide use by drivers, because they find it of benefit in optimising routes under congested conditions and in estimating journey times. Roadside variable message signs are an outmoded technology, providing too little information, too late to be of much use.
There is picture of a route guidance app on page 38 of the RIS2 document, but no mention of its relevance. There is a statement that ‘During RP2 Highways England will work with Transport Focus [a consumer body] to investigate future opportunities to make more granular information about delay on the SRN publicly available. We anticipate that this might include reporting on a regional basis, journeys between conurbations, and maps showing delay across the network on a link-by-link basis.’ Highways England seems totally out of touch with the real world.
The RIS2 mentions the outcome of a number of earlier ‘strategic studies’ that now seem unlikely to lead to much. For the M60 Manchester NW Quadrant, it is concluded that the transformational options identified by the study would have significant adverse impacts on local people and communities, and overall would not provide value for money. The proposed Trans-Pennine Tunnel, improving the route between Manchester and Sheffield, seems unlikely to proceed. The Oxford to Cambridge Expressway project has been paused to look at other options.
In contrast, the A303 Stonehenge Tunnel is to go ahead. Yet the National Audit Office found that transport and economic benefits accounted for only 27% of total benefits; the value of cultural heritage, based on a survey asking people what they would be willing to pay to remove the road altogether, was put by the DfT at 73%, and yet this yielded a benefit-cost ratio of only 1.15 , which in the event is likely to be worse because cost overruns. The NAO noted that the DfT has no plan for the corridor as a whole, and that all the other projects on the route offered poor value for money.
This critique of the A303 route can be generalised to the RIS2 as a whole. Although it is entitled a ‘strategy’, in reality it is a construction programme that is deficient in both economic justification overall and indication of spatial impact of economic benefits. What benefits might we expect, and where? We are not provided with more than vague aspirations.
The Court of Appeal has upheld a challenge to the decision to proceed with a third runway at Heathrow airport on the grounds that the Government’s Airports National Policy Statement (ANPS), which endorsed the runway, was unlawful in failing to take into account the Government’s commitment to the provisions of the Paris Agreement on climate change.
The Government takes the view that Heathrow expansion is a private sector project and so will not appeal against the judgement, leaving open the possibility of later amending the ANPS. This doubtless suites the Prime Minister, who represents a West London constituency under the flightpath and who had earlier been a vocal critic of the airport’s expansion. Abandoning the third runway would also add to the Government’s credibility when hosting the COP26 climate change conference in Glasgow later this year. Meanwhile, the owners of the airport must decide whether an appeal to the Supreme Court would be worthwhile.
The case for increasing the capacity of Heathrow, the UK’s main hub airport, has been based on the needs of business: more direct connections for exporters, facilitating inward investment to the British economy, and boosting London as a world city for doing business. There is no convincing argument for expanding tourism, inbound or outbound, given the need to reduce carbon emissions from aviation.
What is generally overlooked is that most air travel is for leisure purposes. Even at Heathrow, only 25% of passengers are on business trips. So there is ample room for business travel to grow if the demand emerges. Leisure travellers would be displaced to other airports with spare capacity, Stansted and Luton near London, and regional airports beyond. This would happen under the influence of market forces since most business travellers would be willing to pay a premium for the advantages of Heathrow.
Suppose I need to travel to India, to Bangalore for instance. If I’m on a short business trip paid for by my organisation, I’ll fly direct from Heathrow. But if I’m going on holiday, paying out of my own pocket, I’ll shop around for a low-cost flight, expecting to fly with one of the Middle East-based airlines, changing flights at an intermediate hub such as Dubai. I might leave from Heathrow or from Gatwick, Stansted or a regional airport, depending on price and convenience. If demand for business travel to Bangalore grows, leisure travellers who might have flow direct will be have viable alternatives.
Ultimately, growth of demand for air travel will be constrained either by airport capacity or by the need to limit carbon emissions to comply with the Government’s legally binding target of net zero emissions by 2050. One way or another, the cost of air travel is likely to rise, reducing growth in demand.
Hubbub, a UK environmental NGO, has released a report on flying by people in the 20-45 age group, based on a survey sample of two thousand. It found that no less than half the flights by men aged 20-45 in 2019 were for stag parties and a third of flights by women were for hen dos. Hubbub is concerned about the carbon emissions from these flights and the options for reduction by selecting a UK destination. For example, swapping Barcelona for Brighton is the equivalent of going vegan for 2.5 months.
The high proportion of flying for partying is surprising, and reflects the availability of low-cost flights outside the main season for tourist travel. Some increase in the cost of leisure air travel would increase the attractions of domestic destinations, without rather little loss of enjoyment, I anticipate.
Although the private sector operator of Heathrow has a natural commercial interest in expanding its capacity, not all the airport’s users agree. Willie Walsh, chief executive of British Airways’ parent company, has been critical on account of the likely need to cover the cost of construction through higher landing charges. A capacity constraint would allow BA as the dominant airline to raise prices over time, but would also allow the Government to claw back some of the increased profits through a rise in Air Passenger Duty.
In short, we can manage without a new runway at Heathrow. The market will allocate airport capacity to the highest value users, and the UK’s chances of meeting its carbon reduction target will be improved.
The environmental charity Hubbub has released a report on flying by people in the 20-45 age group, based on a survey sample of 2000. It finds that half the flights by men aged 20-45 in 2019 were for stag parties and a third of flights by women were for hen parties. Hubbub is concerned about the carbon emissions from these flights and the options for reduction by selecting a UK destination. For example, swapping Barcelona for Brighton is the equivalent of going vegan for 2.5 months.
An implication of this high proportion of optional leisure flights is to weaken the case for additional runway capacity to accommodate the forecast growth of demand for air travel, in particular the third runway planned at Heathrow. In the absence of increased capacity, growing demand would lead to higher prices in the market for air travel, which would tilt the balance towards UK destinations for leisure trips, to the benefit of the economy of seaside towns and other hospitable destinations. Most air travel is for leisure purposes. There is plenty of airport capacity for business travellers who are willing to pay a premium to command priority over those on leisure trips.
Transport for London has recently published its latest report on Travel in London. At 279 pages, this latest in an annual series is almost certainly the most detailed account of travel behaviour in any city in the world. All credit to TfL.
Table 2.3 shows trip-based mode share. Private transport (very largely car) was responsible for 48% of trips in 2000, declining to 37% in 2015, but thereafter stabilising. Public transport has been stable at 35-36% of trips since 2012, and walking at 24-25% since 2000. Cycling grew from 1.2% in 2000 to reach 2.5% 2018. So the declining trend of car use has ceased in recent years, but it may resume as new rail capacity is opened, particularly Crossrail (the Elizabeth Line). Nevertheless, the target reduction of private transport to 20% by 2041, a feature of the Mayor’s Transport Strategy, looks difficult to achieve.
Section 9.7 discusses the role of licenced taxis and private hire vehicles (PHVs), a topic of much current interest. Taxis (black cabs) have been in slight decline while PHVs have grown substantially in recent years, largely reflecting the entry of Uber into the market. A survey of PHV users in London found that the two main trip purposes were for a night out and to/from airports, but only 28% of PHV trips were for both outward and return legs. App-based PHV users were attracted by specific features: estimate of fare, time for driver to arrive, knowing details of car booked, and estimate of journey time. 30% of PHV users said they had not needed to buy, replace or own a car, which facilitates a shift from individual car ownership.
While a long-term target for reduction in car use has merit in that it shapes shorter term decisions, no Mayor is likely to hold office for anything like the time to reach the 2041 target date. A shorter-term target would allow performance to be held to account. And while the recent experience of London is that a steady reduction in the share of trips by car is compatible with the economic, cultural and social success of the city, sustaining this in the longer term would depend on substantial investment in the rail system that provides a fast and reliable alternative to buses, cars and taxis on congested roads. The biggest challenge for TfL and the Mayor is to find means of financing this investment.
The Greater Cambridge Partnership (GCP) arranged a Citizens’ Assembly, comprising some 60 representative members of the community, that met over two weekends to consider transport options that would reduce congestion, improve air quality and provide better public transport. The Assembly heard evidence on these issues from experts, both independent and staff of the GCP. I was present throughout as an expert advisor. There was extensive discussion by small groups at tables, effectively facilitated by staff of Involve, a charity established to promote public participation in decisions. The GCP was at pains to avoid steering Assembly members to a preferred conclusion, which was achieved, in my judgement.
The context is that the GCP agreed a City Deal with the Coalition Government worth £500m over 15 years, aimed at tackling the transport requirements of a growing city. Cambridge has an historic city centre that constraints both property development and transport provision, so that new businesses, many spun out of university research, are located around the periphery. Travel across the city between homes and employment is impeded by the narrow street network. Cambridge has an effective dedicated north-south busway along a previous rail route, and further such routes are planned. But the problem of the congested centre remains.
The second weekend of the Assembly focused on practical measures, leading to voting on preferred options, the results of which have been published. There was strong support for closing roads to cars, to allow faster and more reliable buses and to encourage walking and cycling, as well as to reduce air pollution. There was also good support for road user charging, to raise funds to invest in public transport and active travel. There was less support for measures to limit or charge for parking, and relatively little preference for no interventions.
The Assembly also voted on a wide range of supporting measures. The most popular was to put in place a franchised bus service under the Mayor, like that operated in London, in place of the present privately operated buses.
The conclusions of the Assembly were a sensible response to the travel problems experienced in Cambridge and the surrounding area – a policy package comprising revenue generated from motorists to support investment in public transport and active travel, plus more road space for these purposes. The GCP is likley to find it difficult to reject this outcome, not least because the funding from the Government comes in tranches that have to be justified by showing progress towards tackling the problems for which the funding was promised.
More generally, this experience indicates that a Citizens’ Assembly may be a more effective means of carrying forward policy in problematic areas, particularly where conventional consultation exercises are likely to stimulate more negative responses from those who believe they would be adversely affected while those who may benefit tend to stay silent.
Breaks in trend
The title of my new book, ‘Driving Change: Travel in the Twenty-First Century’, reflects both the observation that there have been important changes in travel behaviour as we moved from the last century to the present, as well as the possibility that new transport technologies will make a difference to how we travel.
We have nearly half a century of time series data from the National Travel Survey that shows little change in both average travel time (close to an hour a day) and trip rate (about 1000 a year). In contrast, the average distance travelled displays two distinct phases: growth from 4500 miles per person per year in the early 1970s to about 7000 miles by 2000, after which growth ceased. Most travel is by car, so, as expected, car use per capita ceased to grow at the turn of the century, which is also the case for other developed countries. Such cessation of growth of car use has previously been called ‘peak car’, but a better term would be ‘plateau car’ since there is little evidence of a decline in per capita distance travelled.
Growth in average distance travelled was a consequence of higher speeds made possible by the growth of car ownership, supported by road construction. The proximate cause of cessation of growth in car use was the cessation of growth of household car ownership, which increased from 14% in 1951 to 75% by 2000, after which growth ended. A number of factors contributed to the break in the growth trend of car ownership. Population growth in cities, where alternatives to the car are viable, reflected both a shift in the economy from manufacturing to services that tend to be located in city centres, as well as the attractions of city living for young adults, whether studying or in employment.
In successful cities, exemplified by London, car use has been constrained by the capacity of the road network while the travel needs of a growing population have been accommodated by investment in rail. Increasing population density shrinks catchment areas for retail businesses and public services, so making active travel and public transport acceptable alternatives to the car. Car use in London peaked at around 1990 when 50% of all trips were by car, subsequently falling to 36% at present, with the Mayor’s ambition to reduce to 20% by 2041. Increasing population density gives rise to agglomeration benefits – economic, cultural and social – such that declining car use is associated with increasing prosperity. Other cities have a choice: whether to accommodate the car on account of its attractions as a means of mobility; or whether to push back the car to encourage interactions between people.
While car use per capita ceased to grow at the turn of the century, rail passenger numbers went in the opposite direction, doubling over a 20 year period, a consequence of the growth of employment in business services in city centres, congestion on the roads, and investment in the railway by both the private sector train operators and the public sector Network Rail.
The breaks in trend in both road and rail use pose problems for modellers and forecasters. Such breaks reflect changes in travel behaviour, hence historic relationships (elasticities) cannot be assumed to apply. Moreover, the invariance in average travel time observed in the National Travel Survey findings indicates that the benefits of transport investments are not time savings as conventionally assumed. Rather, people take advantage of higher speeds to travel further, to have more choice of destinations, services and opportunities. In short, the benefits of investment are improved access, which is generally subject to diminishing returns. So the conventional four-stage transport model that generates time savings as the output in ‘do something’ cases does not validly represent the changes in travel behaviour that result from an investment.
A feature of travel in the twenty-first century is the impact of new technologies. What impact may we expect on travel by old-established modes of the rapidly developing, often disruptive, digital technologies? Four new technologies are available, or becoming so. Electric propulsion eliminates tailpipe emissions, good for urban air quality and mitigating climate change. Digital navigation can improve the efficiency of our travel and reduce uncertainty and anxiety. Digital platforms allow more efficient matching of supply and demand, exemplifies by ride-hailing taxis such as Uber. And autonomous vehicles may reduce costs for conveyances that otherwise would have a human at the wheel, but may add to congestion as unoccupied private cars make their way to where they are next needed.
The past transport innovations – railway in the nineteenth century, motorcar in the twentieth, modern bicycle in its heyday, motorised two-wheelers in low income countries today – all these allowed a step change in speed and hence in access. In contrast, the new technologies seem unlikely to permit faster travel. Accordingly, they will not be transformational for users, but rather offer incremental improvements to the quality of journeys.
We are therefore in a period of relative stability in respect of per capita travel, which innovative technologies seem unlikely to disturb.
This blog also appeared on the PTRC website.