Over-wide streets? You may regret it
Blog post by Robert Steuteville on 07 Aug 2015
A clear body of evidence has accumulated that narrower lanes are safer on major urban thoroughfares that also include pedestrians.
Another study recently published supports 10-foot travel lanes over the 12-foot common practice on medium- and high-volume urban thoroughfares. Planner and Walkable City author Jeff Speck wrote
an article last fall stating that state DOTs and county road commissions "have blood on their hands" for building over-wide lanes in urban areas. He called for a 10-foot-wide standard, citing a history of studies demonstrating that the
Big Asphalt approach is dangerous.
Speck's words are strong, but imagine the engineer who specifies 12-foot lanes on a major urban thoroughfare with anticipated pedestrian activity and someone is killed. Given the current evidence, does the question emerge as to whether that person's life was put in unnecessary danger? Indeed.
Speck challenged engineers to present evidence that he is wrong--instead, research is confirming Speck's position.
This new study, presented to the Canadian Institute of Traffic Engineers in June, compares Toronto and Tokyo and shows that 10-foot lanes have the fewest crash frequencies and can handle just as much traffic for both cars and large vehicles (trucks, buses). The maximum traffic volume is shown in streets with lanes 3 meters wide (slightly less than 10 feet). "Wider lanes introduce unstable maneuvering and higher interactions, particularly curb lanes," the authors write. Plus, narrower lanes handle greater pedestrian and bicycle traffic.
Given the empirical evidence that favours ‘narrower is safer’, the ‘wider is safer’ approach based on intuition should be discarded once and for all. Narrower lane width, combined with other livable streets elements in urban areas, result in less aggressive driving and the ability to slow or stop a vehicle over shorter distances to avoid a collision.
If anything, the paper understates the safety advantages of narrow lanes by treating the crashes at lower speeds as the same as crashes at higher speeds. One would much rather have 10 or 20 minor fender benders than one severe accident with a disabling injury or death.
Narrower lanes reduce vehicle speed, which has a big impact on fatalities in urban places. The average speed at collision in Toronto, with wider lanes, is 34 percent higher. That is likely to result in accidents of much greater severity. Although accidents appear to go up with lane widths narrower than 10 feet, these accidents are also likely to be less severe. Tokyo has a lot of streets that are narrower than those deemed "safest," yet that city has by far the safest roads while maintaining the highest capacity. That question deserves further study.
