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Re: Pedestrians aren't the only ones who matter.

Posted by Stephen Bauman on Tue Jan 17 11:08:35 2017, in response to Re: Pedestrians aren't the only ones who matter., posted by AlM on Tue Jan 17 09:51:21 2017.

people have more accidents if lanes are only 1/2 foot wider than their vehicle than if lanes are 1 foot wider than their vehicle.

First off, a very small percentage of vehicles are 8.5' wide. Most are 7' or less. This means the conflicts between 8.5' wide vehicles in adjacent lanes are few and far between. Where there are such encounters, both drivers are usually extra cautious and leave their auto-pilot mode.

My gut feel, not backed up by statistics but backed up purely by personal experience

Here's what Sam Schwartz wrote regarding the Williamsburg Bridge in The Rise of Cities and the Fall of Cars, Street Smart, pp. 58-59.

What made the bridge substandard? Its lane widths. The "standard" lane - on interstate highways, on the Cross-Bronx Expressway - was twelve feet wide, but the Williamsburg had lanes that barely exceeded nine feet; at the bridge's towers, the lanes were even narrower. The bridge had no shoulders or breakdown lanes, and had such low clearances that trucks could not use the inner roadways. That meant it wasn't able to move the maximum number of cars into Manhattan as fast as possible.

But we didn't want to move the maximum number of cars into Manhattan. And we sure didn't want them moving any faster when they got there. The bridge was still moving a quarter of a million people back and forth over the East River after eighty-five years, which seemed about right to me...

In order to test the wider-lanes-are-safer-lanes hypothesis, I studied every crash that occurred on the bridge over a three year period and marked each one on a map. If that notion had been true, I reasoned, more crashes would have occurred where the lanes were narrowest, that is at the towers. Just the opposite turned out to be the case. The towers, it turned out, were the safest places on the entire bridge; my explanation is that when traffic lanes get very narrow motorists drive more carefully.


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