With cyclist deaths on the rise in the US, a new study from Rice University recently sought to find out what explains them.
If accidents are usually explained by speeding, distracted driving or infrastructure failures, the research adds a less discussed but potentially decisive factor: imperfect communication between cyclists and drivers, in particular through hand signals.
Research suggests that confusion surrounding arm gestures used by cyclists can increase the risk of collision and lead drivers to react too late or perform a maneuver directly into the cyclist’s path. And, although in many places cyclists are legally obliged to signal, there is no guarantee that these signals are understood by those driving, according to the study cited by .
The team also looked at how different countries define cyclist signs in traffic legislation. He concluded that although many nations resort to similar gesturesrules and expectations are not universal.
To test what drivers understand in practice, the study put participants in realistic driving scenarios and asked them to predict a cyclist’s next action, based on a combination of arm signals, head movement and lane positioning.
The results indicate that drivers rely mainly on hand signals to infer intentions. Other cues, such as the cyclist’s position on the track or a glance over the shoulder, did not increase accuracy.
Eye-tracking data has shown that drivers initially focus on the cyclist’s back to keep them in their field of vision; when movement of the arm or head appears, the focus shifts to these gestures, in an active search for communication “clues”. Yet participants also spent considerable time looking at the face, possibly seeking confirmation through eye contact.
Not all signals worked the same way. “Directional” arm gestures were almost universally understood. But less than a quarter of drivers correctly interpreted the right-turn signal with their arm bent. The gesture to indicate slowing down or stopping, despite being correctly identified by the majority, did not correspond to the sign that many say they would use if they were cycling.
The investigation also assessed the impact of cognitive distractioneven without taking your eyes off the road. In telephone conversation simulations, the ability to predict the cyclist’s intentions decreased: hand signals continued to be the most useful information, but distraction reduced overall performance.
