Driver Performance While Using a Cell Phone 60 

Driver performance when using a cell phone was investigated in terms of visual behavior, longitudinal vehicle control, lateral vehicle control, and reaction to unexpected external events. Drivers’ lane change performance, performance when near intersections, and the effect that drivers using cell phones have on downstream traffic were also investigated. Overall, the results complement the SCE risk findings in that VM subtasks performed on an HH cell phone affected drivers’ visual behavior and vehicle control, while talking on a cell phone did not degrade driving performance.

The root of driving performance lies in how well drivers visually attend to the road in order to perceive events when they occur. Drivers’ visual attention to the forward roadway was

substantially affected by VM subtasks performed on an HH cell phone. Locating, dialing, text messaging, browsing, and ending an HH call all increased the percentage of TEORT compared to baseline. Furthermore, text messaging (M = 23.3 s), browsing (M = 8.2 s), and dialing (M = 7.8 s) all led to substantially longer TEORT durations than when drivers performed PHF and IHF cell phone subtasks. To compare, the largest mean TEORT was 2.7 s when locating a PHF device. Long TEORT durations are a concern as they can degrade drivers’ ability to quickly perceive events in the roadway.

It is interesting that locating an HH cell phone was found to increase SCE risk through the case- control analysis because drivers had a relatively short mean TEORT duration (M = 1.3 s) when performing this subtask. This suggests that drivers may have been selective in terms of when they took their eyes off the road to text, browse, and dial, while they may have used less

discretion when locating an HH cell phone. This is particularly plausible when considering that locating a cell phone to answer an incoming call has an inherent urgency.

When crossing an intersection, drivers properly scanned the intersection 38 percent of the time when not using a cell phone. Their likelihood of scanning the intersection did not change when performing either VM or talking/listening subtasks. When stopped at an intersection, however, drivers that used a cell phone were less likely to scan the intersection prior to advancing. It must be noted, however, that this later finding was produced using 23 observations of drivers stopped at an intersection. As such, there are insufficient data for it to be generalized and a more robust investigation based on a sufficiently large sample size is warranted.

The effects of cell phone use on vehicle control were, in contrast to visual behavior, much less pronounced. Ending both HH and IHF cell phone use was associated with a significantly higher speed standard deviation compared to baseline (as computed over 20 s from the start of subtask). Ending HH cell phone use was also associated with a significantly higher peak deceleration compared to baseline. Although it is possible that drivers braked harder because they were distracted by their cell phone use, it is also possible that drivers chose to end their cell phone conversations when coming to a stop (e.g., in their driveway) or when nearing their destination (e.g., in a parking lot). Another finding was that locating an HH cell phone was performed more frequently when the SV changed lanes. Performing this subtask while changing lanes may be another reason why locating an HH cell phone was found to be associated with an increased SCE risk.

There were two findings that could be construed as evidence of compensatory behavior when using a cell phone. First, browsing was performed at significantly lower speeds than the speeds recorded during baseline. Second, text messaging was performed at significantly greater headways than the headways recorded during baseline. It must be noted, however, that the sample size pertaining to these findings was quite small, making it difficult to generalize the findings. For the most part, drivers did not decrease their speed when performing VM or talking/listening cell phone subtasks. Similar results were found when analyzing commercial motor vehicle speed when drivers engaged in mobile device use (Fitch & Hanowski, 2012). With respect to assessing whether cell phone use affected downstream traffic behavior, the data indicate that a trailing vehicle was more likely to be traveling close (less than 14 m) to the SV when the driver was performing either VM or talking/listening subtasks on a cell phone.

Although a first thought might be that drivers using a cell phone were not keeping pace with lead vehicles, the analyses of vehicle speed and headway did not overwhelmingly indicate that this was the case. What may be more likely to have taken place was that drivers used their cell phones in situations where vehicles traveled closer together (e.g., in stop-and-go traffic). Further analysis should be performed to better understand the contexts in which drivers used their cell phones to properly interpret this finding.

A goal of this study was to investigate the effects of distraction from “just talking” on a cell phone. It was found that talking on an HH cell phone increased drivers’ visual attention to the forward roadway and improved their lane keeping performance. Talking on a PHF or IHF cell phone was not found to impact any of the driver performance measures investigated. An

exploratory analysis did not find drivers’ scanning behavior when crossing an intersection, their tendency to have a rolling stop at an intersection, or their tendency to signal during lane change

was qualified using FACS to explore the potential impact of intense emotional conversation on driving. Emotional conversation took place in 3.6 percent of the samples. Although an

investigation of SCE risk from emotional conversation did not find an effect, the analysis was limited to the small sample size available. Overall, none of the analyses performed in this study found talking on a cell phone to lead to a driving performance decrement.