Autonomous vehicles generally have a lower risk of accidents than those driven by humans, however, there are some notable exceptions, according to a new analysis.
US researchers from the University of Central Florida found that automated vehicles are significantly more likely to be involved in accidents at dusk and when turning. Their findings were published in the scientific journal Nature Communications.
Researchers Mohamed Abdel-Aty and Shengxuan Ding analysed over 37,000 accidents, including 2,100 involving highly or semi-automated vehicles. In semi-automated cars, a driver is always required to control the assistance systems.
The study highlights the safety improvements of autonomous vehicles but points out that clear comparisons with human-driven vehicles are challenging due to limited data on autonomous vehicle accidents.
Researchers compiled accident data from several US databases and compared it with more than 35,000 accidents involving human-driven vehicles.
They found that pedestrians were involved in 15% of accidents with human drivers but only 3% with autonomous vehicles. Additionally, human error, such as inattention or poor driving behaviour, was evident in nearly 20% of human-driven accidents.
Humans are also more likely to cause rear-end collisions, accounting for 79% of such incidents. When autonomous vehicles were involved in rear-end collisions, 72% of the time they were not in automated mode, meaning a human was responsible.
"Compared with the autonomous mode, human drivers may not react as quickly or may not notice the object in time to take appropriate action," note Abdel-Aty and Ding.
The researchers also factored in traffic load, weather, road surface, location, and other accident characteristics to predict accident probabilities in various situations.
Their results indicate that the likelihood of a highly automated vehicle having an accident in the rain is only about one-third that of a human-driven vehicle.
This is partly because autonomous vehicles use radar sensors that can see up to 150 meters ahead, whereas humans may struggle with limited visibility.
However, autonomous vehicles face a higher risk of accidents in poor visibility conditions at dusk and when turning. The probability of an accident at dusk is more than five times higher for autonomous vehicles, and twice as high when turning, compared to human-driven vehicles.
Overall, the researchers view the safety of autonomous vehicles positively: "Based on the model estimation results, it can be concluded that ADS [advanced driving systems] in general are safer than HDVs [human-driven vehicles] in most accident scenarios for their object detection and avoidance, precision control, and better decision-making."