(Side) effects of the rule of the road and neurophysiology on traffic safety: A hypothesis.

Nowadays, the roots of left-hand traffic (LHT) and right-hand traffic (RHT) - including fighting on horse-back and whipping horses that are drawing carriages - are at an all-time low; thus, it is time to assess and appreciate the nexus of road-safety practices and human neurophysiology. We hypothesize that safety of LHT and RHT can be associated with neurophysiology. We summarize scattered empirical research into plausible links between neurophysiological aspects such as handedness, eye movement bias, and hemispheric lateralisation and how safe, in theory, LHT vs. RHT may be for whom. The scarcity and limitations of empirical data into road traffic accidents associated with LHT or RHT are surprising. Even though it was claimed that countries with LHT have lower collision rates than countries with RHT some 50 years ago, we lack informative analyses of traffic accidents in countries with either LHT or RHT which consider plausibly associated neurophysiology. Overall, we predict that LHT (with the driver sitting on the right) is safer than RHT. As 'the rule of the road' and neurophysiology may have important unrecognized "side" effects, we suggest that (and how) this rationale should be tested.