Cities in a driverless future

Which mode should we focus on in 20/30 years time?

Which mode should we focus on in 20/30 years time?

It seems not a week goes by without some story or other about the future of transport – driverless cars. If a new survey doesn’t come out showing support for driverless vehicles growing, or opinion peices opine about how the technology will make HS2 obsolete, with driverless vehicle trials taking place in the UK later this year, it seems the future is automated.

So assuming that driverless vehicles are the future – if not now then in several decades – does this fit in with our aim of creating livable cities? Sebastian Thrun seems to think it will. But that view seems to be…a bit motor-centric to me, a bit of a sales pitch – or a TED Talk as its otherwise called.

But as professionals we should not be reacting to technology or catering for it’s promises, but consider how it can be used as a tool to create what we want to achieve. As I have written before, what we want to achieve is a policy decision informed by the best evidence available. Changing that policy decision in response to emerging technologies and transport modes relies on answering 3 questions:

  • Can the new technology change your desired outcome? If so how?
  • What is the likelihood and impact of that change occurring?
  • If it can result in a less desired outcome, can anything be done about it so you can still achieve what you want?
  • Do you want it to change your outcome?

Fitting driverless vehicles into this is difficult at the moment because robust and independent evidence associated with its technical aspects is still emerging, let alone its impacts and outcomes. Much comment on driverless cars so far has been on the technology, with wider impacts little more than guesswork.

Over the next few posts I am going to be exploring in more detail what the driverless car means for transport policy makers and engineers – what it’s impacts may be and how I feel we should react to this in a way that is consistent with creating liveable cities. I have based this work on whatever evidence there is currently available, but also on two pretty huge assumptions that you are right to challenge:

  • The impacts of driverless cars on their environment are assumed to similar to existing cars, particularly in subjective impacts, though it is accepted that improvements in fuel economy may have environmental benefits due to…
  • Owing to the loss of the human driving factor, operation of driverless cars is assumed to be more efficient than current driving operations.

Also, the evidence that I have used for driverless vehicle operations is based upon the manufacturers claims. Not ideal I know, but if you can point to me where I can find independent verification and tests I am happy to amend this and future posts. And in this post, I start considering how driverless cars could change travel patterns.

Changing travel patterns

Per Square Mile wrote an interesting post recently – and I admit this was part of the inspiration for this post – about how driverless vehicles could affect travel patterns within cities, and how urban areas will react. Transport has a long history of adapting to new technologies that make it easier, more comfortable, safer, and quicker to get around – some adaptations better than others.

The decisions behind travel patterns in our cities are complex on a scale that is almost unimaginable. Every day millions of people take transport decisions that manifest themselves on our transport infrastructure (assuming they wish to travel at all). Our knowledge of what drives these decisions has expanded over the last 20 years away from the traditional engineering approach based upon logical time and cost decisions. Now, there is a general acceptance (at least amongst transport planners I know) that transport decisions are a mixture of both rational and irrational factors. Understanding this is critical to investigating what impacts driverless vehicles are likely to have on travel patterns in our cities.

Rational factors

Rational factors are factors that have underpinned transport knowledge for many years. A transport economist would look at travel choice through two key factors: time and cost. For time, the recent publication of data from the 2012 National Travel Survey reveals something all transport planners have accepted as true for many years; the average time spent travelling per person per day is shockingly stubborn at around an hour a day.

Travel Time Per Day 2012
Total travel time per person per day (hours). Source: National Travel Survey 2012

What has changed over many years is that while people are travelling further, faster, and are doing more trips (particularly by car), their daily travel ‘budget’ has not changed much. A critical argument made by those promoting driverless vehicles is that through make more efficient use of transport infrastructure, journeys will be made more quickly and logically distances travelled be made much further.

I plan to cover infrastructure in more depth in my next post, but there is one critical point to make here. Any infrastructure is constrained by the capacity of its weakest link, and how that link operates. The most obvious examples are junctions, where as well as the physical capacity of the junction itself, there is the ability of software governing signal-controlled junctions to be able to handle competing demands placed upon it (whether by a ‘reservation system’ or otherwise). And that’s before the software capacity of each vehicle is considered.

Substantial time savings for vehicles are found by increasing capacity for vehicles (thus increasing flows), and increasing the speeds at which vehicles are legally allowed to operate. Driverless vehicles may lead to some increases in capacity due to more efficient vehicle operation – after all, more efficient vehicle flow operations at junctions have consistently improved journey times and reliability for vehicles despite their impacts on others. But limits on growth will always remain. Besides, if liveable cities are our aim, should we be looking to put more traffic into them? Answers in the next post.

A common argument is that driverless cars may facilitate smarter travelling, with users using this travel time much better than at present. This depends upon how you classify productive time. Evidence from the University of the West of England on rail passengers and bus passengers indicates use of travel time is complex as people perceive travel time differently, thus it is used differently – some to relax, some to work, some to catch up with friends. Plugging this data straight into WebTAG would reveal that the economic benefit of this time is marginal as it is not seen as an economically-beneficial activity. But that’s not the point. What is economically productive and what is productive to the person are very much different, and people greatly value opportunities to read a book, sleep, or listen to music as it is beneficial to them. So economically speaking, time in driverless cars is likely to be marginally more productive economically than current driving, but may have significant personal benefits. To the driver anyway,

The relationship between journey time usage and journey times is one only just being explored by research. What we know at the moment is that, typically, most people will choose an option they consider to be faster and more reliable – though the value placed on this is different by journey purpose, mode, socioeconomics, and is even poorly understood despite decades of research. This indicates that while people will always seek to use journey time whatever way they can in a way that is productive to them, travel time minimisation is the preferred strategy.

Regarding cost, there has been much comment made upon how driverless cars could facilitate different ownership models that could, in theory, make car ownership more open to those unable to afford it. Data again from the National Travel Survey shows that once a household owns a car, the usage of other modes drops considerably, with transport economists stressing the high sunk costs of vehicle ownership in relation to running costs. Additionally, those with higher incomes are more likely to own cars.

Car ownership

Impact of car ownership on travel by mode. Source: National Travel Survey 2012

The nearest that we have to a low-cost shared car ownership model are existing car clubs. Independent research in car clubs is surprisingly hard to find, with even academic papers on the subject undertaking research by asking the operators of car clubs for their views. The most up-to-date and freely available data that I can find is from the Carplus Annual Survey of Car Clubs 2011/12, undertaken by TRL (it’s free to download from their Library, though you have to register first – which is also free and I highly recommend it). This reveals some interesting results:

  • 43.4% of respondents revealed their car club was a major factor in selling their current car;
  • 59.1% of members said the number of cars they owned had not changed since being a member of a car club, rising to 82.5% for new members;
  • Car club members are more likely to use public transport, walk, and cycle compared to the national average.

Interesting results, but does not answer the key question of whether the low costs of car club membership encourages those who do not own cars to join. Critically, it also doesn’t answer the questions of whether or not greater sustainable transport usage is a cause of car club membership, or simply reflects the attitudes towards these modes demonstrated by members of car clubs.

To be honest, there is not much research into the cost area of driverless cars. The impacts of a shared ownership model are unknown because current data does not reveal whether a shared ownership model influences car use and ‘onwnership’, or is a supplement to an existing largely sustainable travel lifestyle. And if current ownership models are retained, we would expect no change in how ownership affects car use.

Finally, one needs to consider the influence of the urban form upon travel patterns. It is logical that the spatial structure of an urban area should impact upon how people travel around it. But surprisingly the evidence can be somewhat contradictory, and certainly not simplistic. One area where there is strong evidence is distance and centralisation. In large and centralised urban areas, there tends to be longer travel distances, which in turn sees an increasing proportion of car journeys. This is qualified on factors such as proximity of surrounding settlements. With journey distances in urban areas being relatively small…

Proximity to transport networks is also a major factor in mode choice and the dispersal of development. The closer a development is to major transport infrastructure – road, rail, whatever – then people are more likely to access it by longer distance travel and by the modes on that chosen infrastructure. The structure of the highway network can also have a significant impact. In Encouraging Transport Alternatives, Dutch research reveals that when highway networks are laid out with permeable pedestrian and cycling routes, and impermeable and circuitous routes for motor traffic, more people walk and cycle.

filtered permeability

Simple measures to make car driving less convenient. Image from Sustrans

It has been argued that the driverless vehicles will lead to changes in urban forms and travel patterns, much like motorways and railways before them. The reality of this is likely to be much more complex. As we have seen there will always be some constraints on travel patterns. Further change means fundamentally reworking and remodelling our urban areas around the needs of the driverless car. This is clearly possible (you only have to see decades of car-centric planning in the UK to see that), but is a key dependency. And it is also ignores one key thing…

Irrational Factors

Many transport professionals really underestimate the impact of irrationality in decision-making. Whatever we think, we are irrational beings. To give you an example, every morning before you go to work, do you sit down and plan out each alternative way of getting to work in detail? Do you figure out costs, times, likelihood of delays, frequencies for all the modes to come to a reasoned conclusion? Or do you just travel the same way that you did yesterday, or the day before, or the day before that?

People’s transport choices are a mix of both the irrational and rational – no matter how rational we think we are being. Irrationality plays a huge part in travel decision-making. What this means is that our travel patterns are determined as much by our values and attitudes as it is by cost and time. In fact, attitudes have been shown to even trump socio-economic characteristics in determining travel profiles of different areas of the population.

Irrational decision-making does not just affect how people travel, but other decisions that in turn affect how they travel. For example when choosing where to live, attitudes have been found to be more powerful than structural factors like proximity to public transport and housing density. In fact, some argue that residential location has very little impact on travel behaviour compared to personal attitudes. For instance, people who choose walkable neighbourhoods are more likely to prefer walking as a mode of transport.

Strength of habit is also key to modal choice. People who have developed strong habits towards particular modes typically acquire less information on alternatives and are more selective in how they search out this information. Hence why many travel planners argue it is critical to establish new ways of travelling at key life stages, such as changing jobs or moving house – points where new habits are being established. But this in turn can be overruled by the requirements of a particular situation – for example where you need to somewhere by a certain time.

Traffic James

Some do this out of sheer habit

But why does all of this matter to driverless cars? It matters because much of the positive comment relating to them is based upon practicality – more reliable journeys, greater use of journey time etc. Any mode of transport needs to do more than that. Transport is a reflection of values and attitudes (personal and societal), and relates to the sense of self. For any mode to succeed, it needs to satisfy both the rational and irrational part of ourselves (certainly the latter).

Think about car adverts for one moment. They don’t sell you a product by detailing you every aspect of it, they sell you a lifestyle. You remember adverts that best appeal to you (this one’s my favourite, in case you are interested) and forget others. Driverless cars, therefore, do not just need to provide a structural benefit, but a lifestyle one as well.

On this, unsurprisingly evidence on driverless cars is somewhat lacking. There will always be early adopters to any new car presented to the market. Even the current AA polling sees 12% really wanting a driverless car. And so long as there are market conditions that support the wider roll-out of a new product once it is economical to do so. For this, read demand and adequate infrastructure.

Car manufacturers can, and do, sell vehicles that appeal to different people’s attitudes and behaviours. Attitude and behavioural psychology and understanding that is critical to marketing strategies for all major companies. In the UK, DEFRA developed its Framework for Pro-Environmental Behaviours on precisely this. Therefore, there is little doubt that if the market is there, manufacturers can develop and market products that will sell. But that depends on the supporting infrastructure to make driverless vehicles the default choice. This is not just highway networks, but also software and support networks to support the operation of driverless cars. For instance, commonality of standards will be required to ensure that such cars can talk to one another so they remain at a safe distance.

Another factor in irrational decision making is the influence of wider society on people’s values and attitudes. If driverless vehicles – or any other mode of transport – become seen as a social norm, then that will influence both behaviour, and that behaviour being seen as a social norm. Such norms are manifested in a number of ways, either formally (such as by law) or informally through accepted behaviour adopted by a group for which there are reprimands if they are broken. Without predicting future group dynamics, one cannot guess whether driverless vehicles – a major break from current social norms – will develop informally, though again evidence from transport’s past we can suggest this is a possibility. If it didn’t, the horse and cart would still be the chosen method of getting around.

But what possible grounds are there for forcing driverless cars to become the social norm? Legal, clearly, again infrastructure design favouring driverless cars, and the power of advertising are just a few examples. But again this is supposition as to what could happen.


In terms of changing travel patterns, the impact of driverless cars is not certain. My view is that while driverless cars may offer clear advantages to many people, there will always be limiters on what it can achieve. There will always be people where driverless cars are simply not an option for practical reasons (such as travel time) or they do not fit into their personal values and attitudes. Certainly current car users will find driverless vehicles an attractive option for their travel patterns.

In this uncertainty, there is the opportunity to guide driverless vehicles towards travel patterns that meet a policy choice. We can encourage them to become the default transport choice by the decisions that we make that make them attractive subjectively and objectively. A critical component of this will be how we adapt our infrastructure to driverless cars in a way seen fit. 


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