South Dakota's recent speed monitoring report (dated 5/28/96) shows the following numbers for the Interstates:
|Average (50th percentile)||65.6 mph||65.4||66.2||66.0||68.3|
Yikes! Could it be? A speed limit set to the point where it is the safest possible speed, and furthermore, that most people aren't exceeding it?
Then there are the two-lane roads, once posted at 55, now 65:
|Average (50th percentile)||57.6 mph||56.4||57.8||58.1||60.7|
Look at the 85th percentile numbers. When the limit was 55, people were going 7-9 mph over the limit. Now that it's 65, they're going 3 over. For the Interstates, the differences are less but still visible.
Here's something that makes you think. Note that South Dakota's speed-limited drivers are driving faster than the Montana drivers who have no speed limits. About 15% of South Dakota drivers exceed 75, but only 8% of Montana drivers do. Interesting, no?