Citywide Speed Limit Reductions: Creating Violators in the Name of Safety: NMA E-Newsletter #691

By John Carr, NMA Massachusetts Activist

An email claimed that a speed limit reduction in Portland, Oregon “resulted in lower observed vehicle speeds and fewer vehicles traveling at higher speeds.” I was suspicious because it is well known that speed limits and speed limit signs do not have a strong effect on traffic speed. My suspicions were justified. There was no speed reduction.

Look at the science, not the publicity. The paper itself, from Portland State University, reports on the consequences of a speed limit reduction to 20 mph on minor residential streets in Portland. Some streets had been posted 25 or 30. Most of them did not have any signs before.

With the lower speed limit the average speed increased from 21.6 to 21.7 mph. Most drivers used to obey the speed limit. Now most drivers are speeding. These speed limit reductions were on residential streets meant for local traffic only, not arterials and collectors meant for commuters and shoppers. Not even the residents of those streets support the new speed limit.

I don’t give that 0.1 mile per hour increase much weight, despite it being declared “statistically significant,” nor am I impressed by the report that the fraction of vehicles at or below 35 mph increased from 98.9 percent to 99.4 percent. If you have to hold a magnifying glass up to the speed curve and squint to imagine a change, the experiment failed. The data set is not clean enough or complete enough to draw strong conclusions. The scattered measurements taken over the years were clearly not part of a controlled experiment. For example, depending on exactly when the “before” measurements were made NE Ainsworth Street might have been posted 20, 25, or 30, or had no speed limit signs. One or two parked cars on the street on the day speed was measured could have had a large effect on reported speed.

The conclusion most consistent with the evidence is the so-called “null hypothesis”: nothing happened. As a long line of similar experiments already showed. As Boston found out. As Spokane found out.

Advocates of low speed limits like to say they are for pedestrian safety. But in Portland these new limits aren’t being posted where pedestrians are unsafe. Pedestrian, by the way, is a misnomer. In one case a truck ran over a man sleeping in a tent next to an Interstate highway. According to The Oregonian, many people “experiencing homelessness” camp out along busy roads, and most of the Portland pedestrians now experiencing lifelessness come from that community. I bet the residents of streets with less traffic don’t want the “unhoused” living more safely near them.

In modern traffic regulation slogans are more important than science. Mayors chant “Vision Zero” and when it doesn’t work they keep doing it anyway. We keep hearing about the myth of the “vulnerable” road user who is found by government statistics to be much less likely to be injured or killed by a “speeder.”

Making up low numbers in the name of safety does not work. Treating drivers as enemies does not work. But it’s the only tool modern politicians know how to use.

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