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    Self-driving cars will increase road congestion

    June 26th, 2017


    by Ingmar Andreasson

    Many car companies are already testing self-driving cars on public roads. Governments are changing regulations to permit self-driving to support their car industries. In the hype around self-driving, some believe that self-driving cars will solve traffic congestion and eliminate the need for Automated Transit Networks and guideways.

     But manufacturers of self-driving cars will be held liable for traffic accidents and therefore be risk-aversive. Manual cars are driven at unsafe distances most of the time whereas self-driving cars will keep a safe distance. Car manufacturers have a very strong incentive for safety but are not concerned with road capacity. Distances between cars need to be more than doubled to be safe and hence road capacity will be reduced to less than half. Communication between cars does not eliminate risks – the car in front can still have some unforeseen emergency. And it will be a long time before all cars on the road are communicating.

     Not only will road capacity be reduced. Self-driving cars will also generate more traffic. Longer commutes will be acceptable when you can work while travelling. More trips will get made and driverless cars may be sent off empty to park. Some former transit passengers will take a cheap driverless taxi.

     Wherever road congestion is a problem we need to lift trips off the road onto guideways. Driverless taxis on roads or on guideways should always be shared and integrated with other transit modes.

    Ingmar Andreasson

    Prof. Em.andreasson