A trial carried out by Transport for London (TfL) on three stretches of road showed that removing central white lines resulted in a reduction in vehicle speeds.
Explaining the results, TfL suggests that “centre line removal introduces an element of uncertainty which is reflected in lower speeds”.
TfL says that most traffic engineers prescribe white lines “by default without questioning the necessity”. Its study set out to “challenge this assumption” by investigating the effect of not reinstating central markings following resurfacing works.
TfL points to an earlier study by Wiltshire County Council which found that not reinstating white lines led to a reduction in injury collisions and traffic speeds, and to referenced research by TRL which concluded that there are safety benefits to be gained by removing centrelines in 30 mph zones.
TfL reviewed the markings along three routes scheduled for resurfacing, and the white lines/hatching were not reinstated following the works. Before and after speed surveys were carried out at each site to monitor the effect on speed, and at one site a section of centre lines/hatching was retained as a control.
The results showed a “statistically significant” reduction in vehicle speeds – by a minimum of 5.4mph and maximum of 8.6mph – as a result of removing central markings.
Explaining the results, TfL suggests that that centre lines “can provide a psychological sense of confidence to drivers that no vehicles will encroach on ‘their’ side of the road”. It also says “there can also be a tendency for some drivers to position their vehicles close to a white line regardless of the traffic conditions, believing it is their ‘right’ to be in this position”.
The study concludes that “centre line removal introduces an element of uncertainty which is reflected in lower speeds”.
TfL points out that not all roads would be suitable for removing central markings, particularly where the markings highlight a particular hazard.