Whether lattes or lane size, skinny is better

Ten feet lanes, rather than 12 feet lanes are safer and have no effect on traffic flow. Ten foot lanes are an important part of the Pike District’s transformation, especially as we work to add separated bike lanes without changing the overall widths of roads.

According to a recent study, roads with the widest lanes—12 feet or wider—were associated with greater crash rates and higher impact speeds. Crash rates rise as lanes become narrower than about 10 feet, though this does not take impact speeds and crash severity into account. There appears to be a sweet spot for lane widths on city streets, between about 10 and 10.5 feet.

The study also showed that the average crash impact speed is also 34 percent higher with wider lanes, suggesting that wider lanes not only result in more crashes but in more severe crashes.

And according to another study, ten feet lanes have no effect on traffic flow rates. “The measured saturation flow rates are similar for lane widths between 10 feet and 12 feet. So long as all other geometric and traffic signalization conditions remain constant, there is no measurable decrease in urban street capacity when through lane widths are narrowed from 12 feet to 10 feet”.

So, no adverse impact to either capacity or safety when one reduces lanes widths to as little as 10 feet, and we can add bike lanes, wider sidewalks, and perhaps even rapid transit. Now that’s a win-win situation.