AUTONOMOUS VEHICLES

An oft cited benefit of driverless cars is that they will reduce congestion. This study by Tientrakool, Ho and Maxemchuk from Columbia University is one of the first that studies why and how that might be the case. They look at the question from the perspective of highway capacity. They don’t explore the impacts of driverless cars on VMT, which is the other site of the congestion coin. As they show, highway capacity will increase significantly as a result of sensors and vehicle-to-vehicle technology, but most of those benefits won’t be realized until most cars have that technology. A summary of their conclusions has been provided below.

Conclusions:

• Highway capacity will increase 370% when all vehicles have sensors and vehicle-to-vehicle (v2v) communications capabilities.
• Highway capacity increases only slightly if all vehicles have collision avoidance sensors but not v2v capabilities.
• These highway capacity benefits occur by reducing the safe distance between traveling vehicles.

• The highway capacity benefits of sensors and v2v technology depends heavily on the portion of vehicles that have that technology.
• Highway capacity benefits increase slowly as the portion of vehicles with v2v technology increases.
• Highway capacity benefits increase almost linearly as the portion of vehicles with sensors increases.

Key Assumptions:

• Vehicles today travel an average of 1.1 seconds behind the vehicle in front of them on a highway.