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The Old 55 MPH Speed Limit in the U.S. Significantly Reduced Fatalities

The car trip season is fast approaching, if not already underway what with Canadian snowbirds and retirees on both coasts packing up in the United States and driving north back to Canada. They tell of well-maintained highways, heavy traffic around major cities at almost all hours—forget the ‘rush hour’—and an almost non-existent adherence to posted speed limits.

Traffic slows for volume and visible police presence. When it unclogs, bumper-to-bumper left lane clusters form up to speed by the 18-wheelers in the slower right lanes. But even these behemoths are often speeding. Statically for anyone making the trip, the journey should, of course, be ‘crash free’, which is heartening. However, a new report from The Insurance Institute for Highway Safety (IIHS) tells a worrisome story. (The IIHS is an independent, non-profit scientific and educational organization dedicated to reducing the losses from road crashes.)

In 1973, concern about fuel availability prompted the US Congress to pass the National Maximum Speed Limit law requiring states to adopt 55 mph (roughly 88 kph) as their maximum speed limit to qualify for their share of federal highway funds. In 1987, with energy concerns on the wane, states were allowed to increase the maximum on rural interstates to 65 mph. Then, in 1995, a steady push back resulted in the law being completely repealed. Thereafter, speed limits across the country crept higher.

Today, six states have 80 mph (roughly 128 kph) limits; Texas even has 85 mph limits on some roads. (Proponents of higher speed limits always argue that legal limits unaligned with reality are unfair and in and of themselves unsafe, even though higher limits always result in higher over-the-limit speeds.)

Despite safety not having been the priority of the speed limit law, it demonstrated a correlation between speed limits and crash fatality totals: the 55 mph limit dramatically decreased crash fatalities; the partial repeal on the rural interstates increased fatalities on those roads; the full repeal then extended this increase to all interstates.

The IIHS report has looked at all speed limit increases from 1993 to 2013 in 41 states. Nine states and the District of Columbia were excluded because their relatively low vehicle miles per year produced wide fluctuations in their annual fatality rates. It looked at deaths per billion miles traveled by state and roadway type. Accounting for other factors affecting the fatality rate including employment levels, young drivers (ages 16-24), and per capita alcohol consumption, it found that each 5 mph increase resulted in a 4 percent increase in fatalities. On interstates and freeways, the roads most affected by state maximums, the increase was 8 percent.

By comparing the annual fatalities in the 41 states with the expected number if each state’s speed limit had remained unchanged since 1993, IIHS estimates 33,000 additional fatalities over the 20-year period, roughly equal to the most recent nationwide annual totals. And as large a number as it is, 33,000 is likely an underestimate, the report concludes.

“Since 2013, speeds have only become more extreme, and the trend shows no sign of abating,” the report’s author said, adding, “We hope state lawmakers will keep in mind the deadly consequences of higher speeds when they consider raising limits.”

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