When it comes to speed limits, what difference does 5 miles per hour really make?
There are two relevant answers.
For one, it makes you get where you’re going a little bit faster. On the 293-mile trip from Ontario to The Dalles, for instance, it makes about a 20 minute difference (4 hours and 11 minutes at 70 mph instead of four and a half hours at 65).
The second, it makes your travel just a little more dangerous if something goes wrong. A 20-year nationwide study by the Insurance Institute for Highway Safety shows that, in a wreck, every increment of 5 mph means a 3.6 percent greater chance of death. That’s because every 10 mph hour doubles the amount of energy released in the crash.
Both answers are dictated by the laws of physics and mathematics. The first is the kind of algebra you might find on a high school pop quiz, the latter a more advanced study that accounts for not only velocity and impact, but safety equipment installed in modern vehicles.
In 2015, the Oregon Legislature with broad bipartisan support voted to increase the speed on many rural highways by 5 miles per hour. The implications — both the efficiency in travel time and the predicted increase in fatal crashes — were known to the legislators.
According to an analysis by East Oregonian reporter Antonio Sierra, in the two and a half years since the limits were raised, fatal wrecks increased by 10 percent (from 60 to 66) on those roads while fatal wrecks on other roads around the state declined by 3.5 percent.
It’s not a conclusive study. It’s a relatively small sample size — 52 months altogether — and doesn’t factor in all the other parts that make a wreck fatal, including whether a seat belt was worn.
It also doesn’t include the cause of the wreck, but that’s not the point of the analysis. Whether a crash was caused by distracted or intoxicated driving, or an unexpected malfunction or obstacle in the roadway, speed always plays a part in how deadly the crash is likely to be. It may seem like a roll of the dice, but there are odds at play.
The Oregon Department of Transportation is doing its own study on the topic, in conjunction with Portland State University, that isolates factors including road conditions and cause of crash. It will create a more comprehensive look at traffic fatalities where speed was a factor.
But we have no reason to expect any surprises. When speeds go up, so do traffic deaths.
The question is, what should be done?
Driving at high speeds is always a risk, whether that’s 50 mph or 100. As safety measures on vehicles get better, we tend to forget exactly how dangerous of a place the road can be.
The Legislature will certainly take note of ODOT’s report, though it didn’t heed the agency’s warnings before the 2016 legislation was put into effect.
The Oregon Transportation Commission has the ability to lower speed limits where it deems a safety hazard. It did so just a few months after the new limits were put in place on two stretches of highway in central Oregon. That group will certainly take a hard look at the study.
Ultimately, safe driving is up to the operators on the road. Paying attention, obeying traffic laws (including speed limits) and maintaining vehicles are all part of it.
But legislators should also be wary of dismissing six additional deaths as merely a statistical anomaly and be ready to honestly evaluate the impact of raising the speed limits.
The big question is whether the higher casualty rate is worth the added convenience.