technology transport

Would driverless cars be better for the environment?

Last week I was with the Royal Society at their Emerging Technologies conference, where we were discussing how various technologies were going to impact society. In the work stream that I was part of, we talked about cultured meats and insect protein, solar with battery storage, and the internet of things. We also talked about driverless cars, particularly the question of whether or not they will be better for the environment.

The early evidence is that they could be, though most of the savings come from the interconnections and business models that autonomous vehicles make possible, rather than the cars themselves.

First, a computer drives better than a human being in almost every situation you can imagine. So they won’t ever be in the wrong gear, or over-revving a hill start. They will accelerate and brake smoothly, and will thus be more efficient drivers. At higher speeds they could drive closer together and reduce energy use through improved aerodynamics, something known as platooning. This would be true of both electric and petrol autonomous vehicles, though almost everyone thinks that electric vehicles will predominate.

Further savings come through coordination to reduce traffic jams. Because driverless cars will be in communication with each other, news of any delays or obstructions would be relayed through the network of vehicles on the road. Cars would know to find an alternative route, or slow down to avoid a build-up of traffic. This would save the wasted energy spent queuing.

A driverless car doesn’t spend time looking for somewhere to park. That might sound trivial, but it depends where you live. Drivers in London spend an average of eight minutes at the end of each journey looking for somewhere to park. That’s a lot of wasted time and energy every year, all contributing to air pollution in the city. Driverless cars could help in two ways here. First, in a connected city the car would know where the free parking spaces are. It would drop you off and then go and park itself, and come back for you later. And secondly, if a car is part of a club or taxi service, it wouldn’t need to park at all – see below.

Driverless cars mean fewer cars on the roads. At least, they should in theory. To really unlock the benefits of autonomous cars you need to drop the idea of personal ownership and consider them a form of public transport, with fleets of shared cars. Not everyone is ready for that, but it makes sense in cities. Cars would pick up and drop off passengers, and move on to the next journey rather than parking up and sitting un-used for 95% of the day. That means that each car on the road is being used, and we need fewer cars overall.

If we go with all of the above, then we may end up with whole new types of car. If a high number of the cars in a city were autonomous, and the roads were as safe as we hope they will be, then cars can be built completely differently. We currently design cars to carry half a tonne of heavy metal in the form of a combustion engine. They need a sturdy chassis to carry it, and steel reinforcement in case they’re hit by another car. But in a city full of small autonomous EVs, you could make them much lighter without compromising on safety – and of course the lighter a car, the less energy you waste moving the vehicle rather than the people. Amory Lovins has been predicting lightweight plastic cars since the early 90s, but it’s only now that they look viable.

However, this is mostly conjecture. What we can’t really quantify just yet is the rebound effect. Imagine that we got the best case scenario out of this technology – smart connected cities running fleets of shared cars available on demand, all seamlessly integrating with each safely and reliably. Would we take more or fewer car journeys do you think?

Or imagine that driverless cars were more like living rooms, as some people suggest. If cars were comfortable and social places, would you be more or less likely to take them on long distance journeys? Speaking of longer journeys, computers are better drivers than people and could be trusted with higher speed limits, right? So let’s make it 80,90, or 100 MPH on the motorways.

I suspect that if autonomous vehicles deliver on their promise, there’s a good chance we’d take more journeys, and eliminate any savings. We’ll choose them over buses and trains, both of which are more sustainable forms of transport. And we’d want higher speeds, and claw all those efficiency measures back again. Studies in Britain and America suggest they may raise demand for car travel, and ultimately end up worse for the environment.

At this point, neither scenario is inevitable. Much will depend on how we regulate and plan for autonomous vehicles. They appear to be on the way, whether we like it or not, and if we’re complacent about it we could end up with an even worse car culture than we have today. But If we are aware of the risks, we may be able to ensure that we maximise the efficiencies.


  1. How about driverless buses that pick people up to order (via the internet or a mobile phone “app” and adjust their routes according to demand instead of having prearranged routes? Many fewer vehicles needed and less anti-social/atomising than cars.

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