Protective or Not?

There is general consistency in research results on visual distraction and on visual-manual distraction. Visual tasks involving long periods of glance are negative for driving performance and negative for safety, while visual-manual tasks such as texting are particularly harmful to the safer performance of driving. As regards cognitive distraction, there is no such general consensus. Simulator studies have consistently shown that even hands-free phone conversations impair driving performance, while naturalistic studies conducted on real-world driving have generally shown that cognitive distraction in the form of hands-free mobile phone conversation is “protective”, i.e. reduces risk as compared to baseline driving without such conversation. This paper attempts to square the circle, and assess whether cognitive distraction can indeed make driving more safe. It reviews both the simulator and naturalistic studies as well as those that have analysed accident data, and seeks to solve the puzzle of apparent contradiction between the various research methodologies.