Charlotte Leis

December 8, 2017

Share the Road

Self-driving cars may make intersections less dangerous and more efficient. By communicating with an “intersection master,” AVs might be able to navigate intersections without stopping or hitting other cars. This video from the University of Texas shows how that could work:

But there are some essential aspects of intersections that these designers have utterly ignored – other street users. This intersection design does not seem possible if there are non-AV road users like bikes.

Uber is already having issues with bikes in San Francisco. When making right turns, the Uber AVs “posed a direct threat to cyclists” by illegally and unsafely moving into bike lanes. One proposal for making AV-bike interactions safer is to require bikes to be outfitted with sensors just like AVs are, and then having the bike communicate with the AV. But if AVs can’t navigate city streets safely on their own, the solution is not to force other road users to make up for what the AV lacks.

AVs are not all bad for bikes, however. The extra cautions AVs take compared to human-driven cars reduce the risk of car-bike crashes. AVs aren’t good at the nuances of bike-car interactions, like when bicyclists stop at stop signs but maintain the body language of a moving biker. But since the default AV reaction to uncertainty is caution, the inability to interpret nuances is more annoying than dangerous.

AVs can also reduce the risk the risk of car doors opening into bicycle paths, causing the bikes to crash (a phenomenon known as dooring). AVs could reduce that risk by preventing passengers from leaving the car until the bike lane is clear.

Dedicated bike infrastructure – think cycle tracks, not just bike lanes – could reduce the number of bike-car interactions, but until that happens AVs will need to learn to interact with bikes. This is made more difficult because bikes don’t follow the same laws as cars. In all states but Idaho, bikes are treated like cars and are required to stop at stop signs and red lights. Bikers break those laws so often, however, that when they start to follow them drivers get frustrated and confused.

The relationship between cars and bikes on roads is a barrier to mass-adoption of AVs, but it’s a barrier that has a relatively simple solution (although not necessarily one car-addicted Americans will like). Shifting more road space from cars to bikes could reduce the number of car-bike interactions and make trips more pleasant for everyone. Vancouver has started to accept bikes as an important form of transit, and has made biking a much safer experience.
Charlotte Leis
Urban Studies