Driverless vehicles may well cut congestion but could also stimulate more demand for road travel

Driverless vehicles may be more efficient but could offset any reduction of congestion by creating more travel demand says Kristin Olson, senior transportation planner, Arup

There has been much speculation about the way in which driverless automobiles will shape the future city. While there appears to be a growing consensus that driverless vehicles are part of our urban future, what is less clear is how travel demand and congestion on the road network will change in response.

One common claim is that driverless vehicles will reduce congestion. The logic goes like this: Driverless vehicles will be more efficient travelling through intersections as vehicles communicate with each other instantly about which vehicle should turn next. They will be able to drive much closer to other vehicles on the road. And they will be able to accelerate and decelerate more quickly and safely.

All of this, it’s argued, will increase capacity and reduce congestion. However, I am more cautious.

First, increasing the capacity of the road has been shown in most cases to be an ineffective means of addressing congestion. Typically, when the capacity of a road is increased through additional traffic lanes, congestion is eased only briefly.

This is because easing congestion reduces travel time, which results in increased demand for travel and so demand goes up until the road is congested again. Where increasing capacity has successfully eased congestion, it has been in places where there is lagging or even declining economic activity.

I do not believe that unlocking road capacity through widespread adoption of driverless vehicles would be any different to providing additional traffic lanes. I doubt there would be any longer-term impacts on congestion.

Second, all things being equal, I anticipate that driverless vehicles will increase the demand for travel. They will open up the road to people who had previously couldn’t operate a vehicle: children, individuals with visual impairments, and many seniors and others with health issues that currently restrict their ability to operate a vehicle.

Third, as cars become less of a status symbol, and as the popularity of shared ownership and subscription-based mobility rises, auto manufacturers are increasingly focusing on the comfort and amenities inside vehicles. Wi-Fi, sound systems, comfortable seating, easy access to social media, and anything else that makes being in the vehicle as comfortable as possible – or even desirable – is the goal.

In this context, the whole experience of congestion might shift dramatically: instead of feeling enraged by traffic delay and the ensuing lack of productivity, you could simply use the Wi-Fi, continue working, make calls, or engage in social media much as you would at the office or home. Congestion might not even be that much of a hassle if only because people won’t experience it in the same way.

It’s hard to say how driverless vehicles will really affect travel demand and congestion. I suspect that any increase in efficiency or capacity will be exceeded by the increase in demand.



If you would like to contact Bernadette Ballantyne about this, or any other story, please email bernadette.ballantyne@infrastructure-intelligence.com:2016-1.


I think that the only thing that is certain is that driverless cars will radically impact on our transportation. I agree that the impacts beyond this are uncertain, but it seems probable that car ownership will cease, we will work more effectively when commuting, our whole travel patterns will change. Of course car numbers will massively increase, at least cars moving will, though total numbers may drop as a car spends more than 95% of its time parked. This will become very different. However the configuration of our roads will change, as we can get more vehicles in the same width as well as closer together. What we need to do is to work out how to make infrastructure far more flexible and adaptable so that we can respond to whatever transport and people demand. At the moment this does not seem to be on our radar, and we continue to simply build based largely on history and past trends. The implications for our rail network are even more difficult to foresee, but it seems unlikely that we are going to want to sit (or stand) in trains like we do today, nor are we likely to tolerate the way interchanges work. I expect that all of these matters will also impact on urbanisation with smaller cities perhaps becoming more attractive than large or meggs cities.
The mass adoption of quite high end technology suggests to me that it will be dominated by a car sharing model. If it is a majority car share model I would think that people will have to pay more to travel at peak times and less at none peak. This may go someway towards balancing demand and congestion. On the subject of the increased demand for travel, cost of fueling the transport will always act to reduce demand. Hopefully there will be an increase in lift sharing journeys and I would also hope that governments will put sustainability policies/taxes in place to encourage this.