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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 emerg

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.

to3m 12y ago
I would imagine that fire engines and the like will rely more on traffic getting out of their way than on greater overall throughput.
eridius 12y ago
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.
slyall 12y ago
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&uid=2&uid=4&sid=21104886088563 http://www.jstor.org/discover/10.2307/25469783?uid=3738776&u... http://www.cues.fau.edu/cnu/docs/Ex-Urban_Sprawl_as_a_Factor_in_Traffic_Fatalities_and_EMS_Response_Times_in_the_SE_US-Lambert-Meyer.pdf http://www.cues.fau.edu/cnu/docs/Ex-Urban_Sprawl_as_a_Factor...
julespitt 12y ago
When speed increases, the safe distance between cars increases as well, therefore reducing overall throughput.
- seanmcdirmid 12y ago
  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.

to3m 12y ago

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

eridius 12y ago

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.

slyall 12y ago

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&uid=2&uid=4&sid=21104886088563 http://www.jstor.org/discover/10.2307/25469783?uid=3738776&u... http://www.cues.fau.edu/cnu/docs/Ex-Urban_Sprawl_as_a_Factor_in_Traffic_Fatalities_and_EMS_Response_Times_in_the_SE_US-Lambert-Meyer.pdf http://www.cues.fau.edu/cnu/docs/Ex-Urban_Sprawl_as_a_Factor...

julespitt 12y ago

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

seanmcdirmid 12y ago
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.