Should Pedestrians Wear Radar Reflectors So Self-Driving Cars Can See Them?

Welcome to our autonomous future.

man carrying flag
A flag is not good enough for a self-driving car.

By Justin Sullivan/Getty Images

We have often complained about the campaigns to shift the responsibility for squishing pedestrians from the driver to the walker, whether it is a "do the bright thing" campaign or making pedestrians wave flags when they cross the street. We are not supposed to go out and at night without reflectors, vests, and flashlights or we deserve what we get. And if you think that is bad, you ain't seen nuthin' yet.

Treehugger emeritus Matthew Sparkes, now writing for New Scientist, points to a study out of Princeton University which proposes REITS (Reflective Surface for Intelligent Transportation Systems) to make pedestrians visible to self-driving cars or autonomous vehicles (AVs).

Radar doesnt do a very good job

Zhuqi Li et al

AVs use various systems of cameras, lidar, and radar to detect humans and other nuisances in the roadway, but which have proven to be a much bigger challenge than expected. Lidar (a sensing method that uses pulses of laser light) doesn't work well in rain or fog, and radar works by detecting radio waves bounced back from an object that intercepts the beam, and soft mushy human bodies do not do a very good job of this.

There are a number of solutions to the problem. One AV industry executive noted a few years ago that pedestrians have to be trained like they were a hundred years ago with cars, to keep out of the way of AVs. "We should partner with the government to ask people to be lawful and considerate." Others have proposed criminalizing people who walk in front of AVs, taking a photo and sending it to the police department. Needless to say, most people who walk object to these ideas.

Zhuqi Li and his team from Princeton generously assume that the car should do the work and helpfully propose that pedestrians wear this reflector so that the radar can do a better job. It is "a multi-antenna design, which enables constructive blind beamforming to return an enhanced radar signal in the incident direction." They estimate that the AV would detect the pedestrian 3.63 times as far away.

Reflection when wearing suit

Zhuqi Li et al

This is not a regular mirror, but a Van Atta array, where a signal is received, amplified, and fired back in the direction from whence it came. They are more expensive and require electronics and power, but are much more effective, especially when there are a lot of cars and a lot of pesky pedestrians. However, this also makes it much more expensive; according to Sparkes,

"The prototype device consists of a single printed circuit board with several small antennas and costs $2000 to manufacture. The team believes this cost can be reduced with mass manufacturing and that it can be used as a safety device on the outside of vehicles, road furniture and on clothing for pedestrians and cyclists, in much the same way as reflective high-visibility tape."

There are many who think this is a terrible idea. Zack Furness of Penn State University, who has written a book about the politics of automobility, notes on Twitter that it's "hard for me to fully articulate the poverty of wisdom and imagination that animates this kind of myopic thinking. Imagine being so hypnotized by techno-bull***t discourses that you lack the basic ability to view human beings, not cars, as those with the real 'right to the city.'"

self driving car interior

Stephen M. Johnson

When we started writing about AVs, the predictions were that by 2020 we were all supposed to be drinking martinis and watching movies in our self-driving cars, and it didn't happen; there are not only technical problems but also legal and social issues that take much longer to resolve. We have quoted a car expert comparing Level 5 autonomy, where the car can drive anywhere on its own, to "a manned mission to Mars ... You need latest-generation mobile infrastructure everywhere, as well as high-definition digital maps that are constantly updated. And you still need near-perfect road markings,” 

And, evidently, radar reflectors on every human being.