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Tests Show Higher Speed Limits Don't Kill

Matter-Eater Lad

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Humans are marvelous at self-organization -- it's how we get nomadic tribes and cities like Tokyo, it explains how New Yorkers avoid each other and actually get places on the sidewalks in midtown, and it leads to things like book-of-the-month clubs. It also explains how we avoid accidents at intersections when the red light stops working. Given our choice, we will find ways on our own to live together, mostly safely.


The blackest and whitest versions of the speed limit debate put "Speed Kills!" on one side and "No it doesn't!" on the other. Because both sides have metric tons of paperwork to prove their positions, the chance that the debate will be settled in our lifetimes is intergalactically remote. A recent speed limit trial in Utah, though, appears to be another scrap of evidence for those on the side of "No it doesn't."


"The Utah Department of Transportation (UDOT)," began an article in TheNewspaper.com, "announced last week that the experimental increase in the state's maximum speed limit to 80 MPH has been a success in terms of safety. UDOT Deputy Director Carlos Braceras testified before the state Interim Committee on Transportation that that there has been no increase in accidents as a result of the higher number printed on the speed limit signs on certain stretches of Interstate 15."


Barring any other considerations, a speed limit is determined by studying the behavior of 85% of traffic over a given stretch of road. That 85th percentile is given credit for self-organizing into a group that moves at the safest and most efficient speed. There doesn't appear to be any clear-cut study that proves this, but it has been gospel for so long that it is now the precedent for deciding limits, and in some instances, court cases.


The UDOT measured the speed of that 85th percentile before and after raising the limit. When the maximum allowable speed was 75 mph, it reported most drivers doing between 81 and 85 mph. Given another five miles an hour to legally play with, a year of observation found that most drivers doing between 83 and 85 mph. The vehicular carnage that some suspected didn't materialize, nor did drivers automatically begin driving 90 or 95 mph. As was the case before the limit was raised, people liked going about 85 on the stretches of road in question. They probably also enjoyed not getting tickets for it.


Without taking sides, Utah's findings do match recent findings and decisions in other states. When the North Texas Tollway Authority (NTTA) studied speed limits on six sections of roads it maintains, it changed the speed limits on five of them: one saw a decrease of 5 mph, the other four were increased from 5 to 10 mph.


When Montana had no daytime speed limit, fatalities not only went down but Montana recorded the state's fewest road fatalities during that period. Internationally, the number of fatalities per billion vehicle kilometers has been higher in the U.S. for about the past seven years than anywhere in Western Europe except for Ireland. Even Germany and its unrestricted autobahn suffer fewer injury incidents than the U.S.


Outside of the safety issue, some folks have chosen to see Utah's DOT results as proof that higher limits mean less speeding. That could be cheating a bit by using a relative definition of speeding -- people didn't actually slow down, the law just happened to catch up to them. Almost.


It could be more informative to see the issues of speeding and safety as follow-on effects of the widely held but as-yet-unproved instinct at work: 85% of people found a speed range at which they can drive mostly safely. And as that range didn't really change after the posted limit was changed, we can assume that the instinct for a safe speed has nothing to do with what the posted and enforced speed limit happens to be.


People want to get where they're going quickly and alive. If the powers that be would set limits more in accordance with that fact, perhaps the national blood pressure – and that of drivers – would flow more efficiently and just as safely. At least, it wouldn't hurt to try it out here and there.


It gets back to that self-organizing thing we've been perfecting for thousands of years. As a herd, we will find ways on our own to live together, mostly safely. Even in the fast lane.



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