Effects of Cell Phone Conversation on Drivers’ Perceptions of Cyclists’ Intentions

Abstract

In the last decade, there has been an increase in the number of cyclists killed in traffic collisions. One potential cause of collisions between vehicles and cyclists is drivers’ inaccurate judgments of cyclists’ intentions. Another possible cause for collision is cell phone use, which diverts drivers’ attention from the road. The current study aimed to determine what cues drivers used to make quick and accurate judgments of intent and whether talking on a cell phone impacted drivers’ abilities to accurately predict cyclists’ intentions. Our results revealed that only arm signals significantly impacted driver judgments; road position and head movement did not. The results also showed that simulated cell phone conversations led to less accurate responses, highlighting the dangers of talking on the phone while driving.

One of the potential causes of collisions between road users is inaccurate judgments of intentions ( Bjorkman et al., 2008 ). Such events can occur when communication between a driver and a cyclist is unclear ( Drury & Pietraszewski, 1979 ). The National Highway Traffic Safety Administration recommends that cyclists use specific arm signals to let other road users know they intend to turn or stop (National Highway Traffic Safety Administration, n.d.). To turn right, the cyclist should extend their right arm straight out or bend their left arm up at a 90° angle. To turn left, the cyclist should extend their left arm straight out. To stop or slow down, the cyclist should bend their left arm 90° downward. In certain states, cyclists are required by law to use arm signals to communicate ( Transportation Code, 1995 ). In addition to arm signals, road users have reported using informal signals such as head movements and position on the road to predict a cyclist’s intention ( Drury & Pietraszewski, 1979 ; Hemeren et al., 2014 ). However, prior work has not examined the effect of these cues on drivers’ judgments of cyclists’ intentions. Therefore, our first aim was to determine which cues allow drivers to correctly predict cyclists’ intentions.

Another cause of collisions is cell phone use; in the last 12 years, there has been a 45% increase in the number of cyclists killed in traffic collisions with a distracted driver ( Fatality Analysis Reporting System, 2024 ). Research has shown that cell phone conversations are cognitively demanding tasks and divert a driver’s attention away from the road ( Strayer & Johnston, 2001 ). Therefore, our second aim was to identify whether talking on cell phones impacts drivers’ abilities to accurately predict cyclists’ intentions.

Sixty participants viewed video clips of a cyclist displaying a combination of cues, including arm signals (none, left, right, alternative right, or stop/slow), head movement (none, look right, or look left), and position on the road (left, right, or center of the lane). After the clip ended, participants were asked to report what they believed the cyclist intended to do (i.e., turn left, turn right, stop, or go straight). Half of the participants completed an additional Last Letter Task (LLT), which simulated a cell phone conversation ( Strayer & Johnston, 2001 ).

Two logistic regressions were performed to identify whether intention prediction accuracy depended on arm signals, head movement, position on the road, and the LLT. Regardless of the LLT condition, drivers who saw a straight right turn arm signal were more likely to predict the cyclist’s intentions correctly than drivers who saw a bent right turn arm signal or the stopping/slowing arm signal. Furthermore, talking on a cell phone led to a smaller likelihood of correctly predicting the cyclist’s intentions compared to not talking on a cell phone. Lastly, both head movement and lane position did not affect a driver’s likelihood of correctly predicting a cyclist’s intentions.

The results showed that only arm signals impacted driver judgments; road position and head movement did not. This suggests that cyclists should avoid relying solely on head movement and road position when communicating with drivers. Results also showed that cyclists should avoid using bent-arm signals (i.e., stop/slow and right turn), as these signals lead to a smaller likelihood of correctly predicting the cyclist’s intentions. Current transportation laws should modify these bent-arm signals to make communication clearer. Future research should determine the most effective arm signal to communicate stopping/slowing down and consider removing the bent right turn arm signal and the potential consequences of doing so. Encouraging cyclists to use arm signals that are clearly understood by drivers could reduce confusion and potential collisions in the traffic environment.

The finding that simulated cell phone conversations led to less accurate responses highlights the dangers of talking on the phone while driving. Drivers should avoid talking on the phone to increase the likelihood that they will predict cyclists’ intentions accurately. These findings have practical implications for improving road safety and emphasize the importance of clear communication between cyclists and drivers. Further, the impact of a simulated cell phone conversation on drivers’ abilities to predict cyclists’ intentions contributes to our understanding of the effects of distractions on predicting intent. Standardizing arm signals and raising awareness about the dangers of distracted driving could help mitigate collisions between drivers and cyclists and improve overall road safety.