[TorqueDog]

Originally Posted by Resolute 14

Raising the official speed limit will likely only push the unofficial speed limit up to 130-135. Doubt the province wants to go for that, so the only real way there can be an official speed limit increase is if it includes a long and concerted crackdown on speeding. The end result will be no change to highway speeds from today, but a lot of pissed off people with big fines.

Report done by the US D.O.T. back in June of 1996: http://www.motorists.org/speed-limit...ising-lowering
PDF of the study: http://www.motorists.org/speed-limit...g-lowering.pdf

Item #5 is of direct relevance to your post.

Summary of Findings
The pertinent findings of this study, conducted to examine the effects of lowing and raising posted speed limits on nonlimited access rural and urban highways, are listed below. NMA's comments and clarifications are in [italics]

1. 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.
2. When sites were grouped by the amount of speed limit change, the differences in percentile speeds for each group were less than 1.5 mi/h (2.4 km/h), irrespective of whether the speed limit was lowered or raised or the amount that the limit was changed. The average change in percentile speeds at sites where limits were lowered and at sites where speed limits were raised was less than 1 mi/h (1.6 km/h).
3. The small differences in before and after speeds were statistically significant due primarily to the large sample size collected.
4. At 34 locations, existing speed limits were posted within 5 mi/h (8 km/h) of the 85th percentile speeds. When speed limits at these sites were lowered more than 5 mi/h (8 km/h) below the 85th percentile speed, the mean difference in percentile speeds was less than 1 mi/h (1.6 km/h). [In other words, lowering the speed limit does not mean traffic will slow down.]
5. At 21 other locations, existing speed limits were posted more than 5 mi/h (8 km/h) below the 85th percentile speeds. When the agencies raised the limits to within 5 mi/h (8 km/h) of the 85th percentile speeds at these sites, the mean difference in percentile speeds was less than 1 mi/h (1.6 km/h) [In other words, raising the speed limit does not mean traffic will speed up.]
6. 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. [Higher limits mean a greater number of drivers traveling at the limit instead of over it.]
7. Based on the free-flow speed date collected for a 24-h period at the experimental and comparison sites in 22 states, posted speed limits were set, on average, at the 45th percentile speed or below the average speed of traffic. [This means that, on average, only 45 percent of us abide by present speed limits.]
8. Only minor changes in vehicles following at headways of less than 2 s were found at the experimental sites with similar before and after traffic volumes. [People don't follow any closer when the limits are raised.]
9. The indirect effects of speed limit changes on a sample of five contiguous and adjacent roadways were found to be small and insignificant. [Changing a speed limit on one road does not mean that speeds on all roads nearby will change as well.]
10. 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. [Lowering the speed limit does not reduce the number of crashes.]
11. There is not sufficient evidence, in this dataset, to reject the hypothesis that total crashes changed when posted speed limits were raised more than 5 mi/h (8 km/h) below the 85th percentile speeds. [Raising the speed limit does not increase the number of crashes.]