mobility ecosystem

Narrower Lanes, Safer Streets

Of all street design elements, no other has evoked as much bafflement, incredulity and conjecture as the safer range of travel lane width. Traditional traffic engineers argue wider lanes are safer. Supporters of the livable street concept passionately promote the safety benefits of a relatively narrower lane width. Recent claims are emerging in favour of the livable street approach. However, neither side has yet produced any empirical evidence that links crash frequency or severity to lane width. This paper attempts to address this disquieting quandary.

After 17 years research, scanning more than 3,000 articles/papers and over 20,000 hours of work, I finally concluded in my recent conference paper that oversized infrastructures such as wider lanes increase crash rates. On contrary, narrower lanes (3.0~3.2m) carries more traffic, demonstrates better safety records, and equally comfortable for large vehicles (for volume ~5%) while leaving enough space for pedestrians and cyclists.

Figure 1: Relationship between lane width and crash rates
Figure 2: Distribution of lane width for Tokyo and Toronto

Pedestrian volume declines as lanes widen, and intersections with narrower lanes provide the highest capacity for bicycles.

Figure 3: Distribution of traffic capacity (per lane per hour) demand and lane width (Toronto)

Finally, wider lanes (over 3.3~3.4m), the predominant practice of Toronto regions, are associated with 33% higher impact speed rates and higher crash rates, despite higher traffic volumes and one-sixth the population than that of Tokyo. Most surprisingly, the findings were identical for two large cities located on opposite sides of the planet: Toronto and Tokyo.

Figure 4: Large vehicle usage as per lane width (Toronto)

Evidence shows how practicing #engineering based on evidence keep Tokyo streets safer than Toronto. Given that the empirical evidence favours ‘narrower is safer’, the ‘wider is safer’ approach based on personal opinion or intuition should be discarded once and for all.

Disclaimer: The views expressed in this article are those of the author and do not necessarily reflect the views of the Metropolitan Tokyo Government and City of Toronto.

Full paper can be downloaded from: