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.

• This article can also be read in Arup Thoughts