Quote:
Originally Posted by LeanBurn
Having driven in Utah just recently...aren't they already going 80+ already? That I-15 in Utah is crazy already...lots of accidents...bumping the limit to 80mph would mean they would just go faster...scary.
My 1997 gas suburban 5.7L easily gets 15mpgUS at 60mph fully loaded with gear and kids in the winter.
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Yes, they generally are going 80+. And no, rasing the speed limit won't significantly alter the speeds they are driving. Changes in fuel costs should be minimal, since speeds won't really change.
Study after study has been made on this topic. Generally, the speed limit should be set at or close to what the 85th percentile of drivers are already driving at. This is probably how Utah determined 80mph for these roads. Changing speeds does not appear to increase or decrease the number of accidents. This does have a LARGE increase in drivers complying with the speed limits.
One of the most well-known studies is this one:
http://www.fhwa.dot.gov/publications...7084/97084.pdf
Here are some of the Key Findings:
• A review of the before and after speed data at each site revealed that differences in mean speeds, standard deviations of speeds, 85th percentile speeds, and other percentile speeds were generally less than 2 mi/h (3.2 km/h) and were not related to the amount the posted speed limit was changed.
• By defining driver compliance as the number or percentage of drivers that travel at or below the posted speed limit, major changes in compliance occurred when speed limits were raised or lowered. However, as reflected in small changes in vehicle speeds, driver behavior did not change, but the standard for measuring compliance, i.e., posted speed limit, changed.
• There is not sufficient evidence, in this dataset, to reject the hypothesis that total crashes or fatal and injury crashes changed when posted speed limits were either lowered or raised.
• There is not sufficient evidence, in this dataset, to reject the hypothesis that total crashes changed when posted speed limits were lowered more than
5 mi/h (8 km/h) below the 85th percentile speeds.
• There is not sufficient evidence, in this dataset, to reject the hypothesis that total crashes changed when posted speed limits were raised to within 5 mi/h (8 km/h) of the 85th percentile speeds.