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Comment by kenjackson | Hacker News Reader

How does traffic speed increase with wider lanes, but capacity doesn't?

How many lives are saved by fire trucks, police, etc... being able to get to/from emergencies more quickly? I feel like experimental data will be much more useful than models to measure the impact of 10' to 12' lanes.

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I read a story just recently that suggested that suggested that since areas with wider lanes have lower density any speedups of emergency vehicles is lost because they one average have to travel a greater distance.

I can't find the original story but here are some papers:

"The findings show that the density and age of a residential area or jurisdiction explain some of the variation in average EMS response times between urban and suburban or exurban locations. Holding other things constant, those who live in more sparsely settled and newer developments tend to have longer wait times for EMS."

http://www.jstor.org/discover/10.2307/25469783?uid=3738776&u...

http://www.cues.fau.edu/cnu/docs/Ex-Urban_Sprawl_as_a_Factor...

These are city streets. Capacity is probably limited by the rate at which cars go through traffic lights (which is probably largely unchanged by 10 vs 12 feet lanes), not by how fast a motorist can accelerate when driving away from a light.

I would imagine that fire engines and the like will rely more on traffic getting out of their way than on greater overall throughput.

When speed increases, the safe distance between cars increases as well, therefore reducing overall throughput.

Actually, more speed also means cars spend less time on the road, so throughput increases still. Bumper to bumper Traffic jams don't mean high throughput. What is most important is smoothness in flow.

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