In answering a reader’s question, Washington State Department of Transportation spokesman Tom Pearce shared how the state arrives at its speed limits. It’s interesting enough to share here, too:
“Based on national standards and state law (WAC 468-95-045), speed limits are set to reflect the behavior of the majority — that is, the maximum speed at which 85 percent of vehicles travel. This follows the principle that reasonable drivers will consider road conditions when selecting their speed of travel.”
It’s one reason the state doesn’t permanently lower a road’s speed limit simply to try and force drivers to go slower.
“Studies consistently demonstrate that there are no significant changes in the 85th percentile’s speed after a revised speed is posted. The idea is to create a ‘realistic’ speed law. This allows the majority of drivers to comply with the law and gives a clear reminder to those who do not, providing an effective tool for law enforcement by separating the violators from the vast majority. It also brings in an element of logic and reason to what may be seen as an arbitrary and often emotional issue.”
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