A decades-old rule lets drivers set speed limits on US roads. That could be changing
Growing safety concerns and a rise in road deaths have prompted states and federal agencies to reconsider the 85% speed limit rule, with studies showing fatality risks increase 8.5% per 5 mph rise on highways.
- Amid a recent spike in road deaths, the Federal Highway Administration signaled that the 85% rule isn't a binding guideline, prompting states to reconsider their speed limits.
- The 85% rule, a longstanding guideline, ties posted speeds to the 15th-fastest vehicle out of 100 in rural roadway studies from the 1930s and 1940s.
- Demonstrating the rule’s impact, the study linked higher speed limits to increased fatalities, as the 85% rule calls for raising the limit to 60 mph, and Seattle’s pilot program saw a 7% drop in 85th percentile speed.
- Amid growing local concerns, Sylvania Township officials asked county engineers in March to analyze Mitchaw Road’s speed limit, only to learn the guideline supports raising it to 60 mph, surprising leaders.
- Developing an alternative, the National Association of City Transportation Officials introduced the ‘City Limits’ formula, allowing safety-driven departures from guidelines.
83 Articles
83 Articles

States rethink a long-held practice of setting speed limits based on how fast drivers travel
Road safety activists and some states are pushing to depart from a longstanding rule that sets speed limits in the United States based largely on how fast drivers actually travel. This is due to the 85% rule, which ties speed…
Outdated rule that lets drivers set speed limits on US roads could be changing amid spike in highway deaths
The 85% rule, where a road’s posted speed is based on the 15th-fastest vehicle out of every 100 traveling it in free-flowing traffic, may be modified or replaced in some states.
States rethink how speed limits should be set
Rose Hammond pushed authorities for years to lower the 55-mph speed limit on a two-lane road that passes her assisted-living community, a church, two schools and a busy park that hosts numerous youth sports leagues. Read more...
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