Mobile phone distracted driving (MPDD) is an ongoing challenge for transport network managers. … Different studies report varying effects of MPDD on crash risk. An epidemiological study found that mobile phone conversations increase crash risk by a factor of four. Asbridge et al. reported that the odds of a culpable crash increase by 70% when the driver is using mobile phone. In the United States, an study of police crash reports showed that mobile phone distraction resulted in 18% of fatal crashes and 5% of injury crashes. Epidemiological studies and police reported data, however, often suffer from underreporting problems and do not record the exposure to mobile phone use, and therefore these estimates may be inaccurate.

Experimental and/or naturalistic studies, on the other hand, are not suitable for estimating actual crash risk as crashes are rarely observed within the study design. Hence, the use of surrogate measures of safe driving performance has been common, but the variety of these measures and the irregular results obtained has impeded a better understanding of the risk of using mobile phones while driving. Moreover, the nature of the relationship between surrogate measures and actual crash risk is poorly understood and evidence is lacking.

This article proposes a systematic framework based on a human-machine system [HMS] approach to identify all of the components and interactions of MPDD so the effects of mobile phone use can be systematically analysed.

—Oviedo-Trespalacios et al.

The framework specifies the impacts of mobile phone distraction as an inter-related system of outcomes such as speed selection, lane deviations and crashes; human-car controls such as steering control and brake pedal use and human-environment interactions such as visual scanning and navigation.

(a) Mobile Phone distracted driving as a HMS. (b) Causal mechanisms of the mobile Phone distracted driving as a HMS. (a) Mobile Phone distracted driving as a HMS. (b) Causal mechanisms of the mobile Phone distracted driving as a HMS. Oviedo-Trespalacioset al. Click to enlarge.

The researchers measured the effects of mobile phone distraction on safety including reaction time and driving performance in the CARRS-Q Advanced Driving Simulator.

The researchers exposed a group of drivers to a virtual road network which included a pedestrian entering the driver’s peripheral vision from a footpath and walking across a pedestrian crossing. They monitored driver performance and reaction times during hands-free and hand-held phone conversations and without.

The study found that the reaction time of drivers participating in either a hand-held or hands-free conversation was more than 40% longer than those not using a phone.

In real terms this equates to a delayed response distance of about 11m for a vehicle travelling at 40km/h [25 mph]. This shows hands-free and hand-held phone conversations while driving have similar detrimental effects in responding to a very common peripheral event of a pedestrian entering a crossing from the footpath.

—Dr. Haque

Dr. Haque said it was the cognitive load required to hold a conversation that was the distraction, not whether or not the driver was holding a phone.

It appears that the increased brain power required to hold a phone conversation can alter a drivers’ visual scanning pattern. In other words, the human brain compensates for receiving increased information from a mobile phone conversation by not sending some visual information to the working memory, leading to a tendency to ‘look at’ but not ‘see’ objects by distracted drivers.

The distraction of a mobile phone conversation is not the same as an in-car conversation with a passenger because the non-driver can alter their dialogue based on the driving environment, for example stop talking when approaching a complex driving situation.

—Dr. Haque

Dr. Haque said the distraction of mobile phone use also had an impact on driver braking behavior; distracted drivers on average reduced the speed of their vehicle faster and more abruptly than non-distracted drivers, exhibiting excess braking

While the driver is likely to be compensating for the perceived risk of talking and driving, the abrupt or excessive braking by distracted drivers poses a safety concern to following vehicles. Again these findings highlight a need to consider mobile phone use laws in response to interventions to reduce rear-end crashes.

—Dr. Haque

Resources

• Oviedo-Trespalacios, Óscar, Haque, Md. Mazharul, King, Mark, & Washington, Simon (2016) “Understanding the impacts of mobile phone distraction on driving performance: A systematic review.” Transportation Research Part C: Emerging Technologies, 72, pp. 360-380 doi: 10.1016/j.trc.2016.10.006