Phantom braking: safety concerns in autonomous vehicles

A new study suggests that autonomous vehicles are not ready to share the road with humans.

A new study suggests that autonomous vehicles are not ready to share the road with humans. Conducted by George Mason University professor Missy Cummings, the study found that driverless cars exhibit “phantom braking” and struggle to follow human driving behavior. These issues result in high collision rates, jeopardizing road safety.

As the principal safety advisor at the National Highway Traffic Safety Administration (NHTSA), Cummings investigated the operations of autonomous vehicles in California to refine the study’s results. She focused her research on three of the state’s leading companies: Cruise, Waymo, and Zoox.

Autonomous vehicle accident rates

The study initially focused on accident rates. Of the three companies analyzed, Waymo had the best results, with approximately 1,000 accidents per 100 million kilometers. Although these numbers are higher than human drivers, who are responsible for 224 non-fatal accidents per 100 million kilometers on non-interstate roads, Waymo’s figures are similar to those of ride-sharing drivers like Uber and Lyft, who have much higher accident rates, close to 1,400.

Cruise and Zoox, on the other hand, had much higher rates, with up to 3,000 and 4,000 accidents per 100 million kilometers, respectively. It’s important to note that these comparisons are not statistically significant, as human drivers travel over 3 trillion kilometers annually, while autonomous vehicles have only traveled millions of kilometers in total.

However, upon finding that accident rates are scientifically invalid, Cummings focused on the causes of these accidents, where she identified concerns that could worry both drivers and pedestrians.

Phantom braking and other issues with autonomous vehicles

In a two-year study of over 200 autonomous vehicle accidents, nearly half of the incidents were rear-end collisions where the autonomous vehicle was hit from behind. Cummings discovered that, in many cases, the autonomous vehicles were at fault due to “phantom braking,” where the vehicle suddenly brakes without apparent reason. This phenomenon occurs because autonomous vehicles often detect non-existent objects, causing abrupt stops.

Phantom braking has led to a dangerous pattern of accidents, especially with trucks, as these heavy vehicles can cause severe damage when involved in unexpected braking. Zoox is currently being investigated by NHTSA for incidents related to sudden braking that caused rear-end collisions.

Cummings notes that humans are often caught off guard by the unexpected decelerations of autonomous vehicles, resulting in rear-end collisions. The study also found that only 10% of accidents were due to the vehicles failing to detect objects, while 50% were caused by the detection of non-existent objects.

The study warns that the consequences of these phantom brakes would be much more severe on higher-speed roads, especially for trucks. While autonomous vehicle technology continues to improve, more research and oversight are still needed.