I am a strong supporter of Strong Towns, and think their analyses of financial and transportation issues is almost always spot on. However, I think there is a blind spot when it comes to speed limits. In a recent broadcast, Chuck Marohn addresses a question from a member about whether it is better to change speed limits street by street, or all at once. In response, Chuck launches into his view that only design changes can control speed. This is the first question in the broadcast, so you can listen from the beginning.

Here is my response:

I have to push back against Chuck’s take on speed limits. Nothing he says is incorrect, but there is an underlying ideology that rejects changing speed limits without changing design, as any part of a solution.

1. This is not about enforcement. I agree that much of traffic enforcement is pretextual, and intended to oppress people of color and low income. I’m not asking for any more enforcement, and am in complete agreement with the current movement towards removing most traffic enforcement from the responsibilities of armed law enforcement agents. And moving speed and red light running enforcement to automated systems. In high risk, high fatality/injury settings, we could even invest in automated enforcement of failure to yield to people in crosswalks, which is a driver behavior that not only kills people walking but intimidates them out of walking.
2. Chuck correctly states that drivers respond to roadway design, and consider what feels safe in setting their own speed. However, he misses the fact that drivers also respond to the speed limit. Drivers are very aware of posted speed limits. I constantly hear drivers say things like “I always go 5 mph (or 10 mph, or…) over the speed limit”. If the speed limit is 25, they will go 30, or 35, not just based on roadway design, but on the posted speed limit. If we lower it to 20, they will go 25 or 30. That is a huge difference (see the fatality at various speeds charts), and should not be discounted.
3. The problem with 85% is not just that it allows drivers to set their own speed limits, but speed creep. If 85% indicates a ‘safe’ speed of 35, and it is posted, then drivers will start going 40, and the next survey will show 40 is the ‘safe’ speed, and so on, ad infinitum. Regardless of the impact on drivers, every increase in actual speeds makes the street less safe for people outside vehicles. Which is why high speeds should be reserved for limited access, designed for higher speeds, roadways. Streets should always be posted for the desired safe speed, no matter the roadway design.
4. I live in a city where, at the current rate of roadway redesign, it will take about 80 years to create a safe system, and in a county where it will take at least 120 years. I am not willing to accept the death and severe injury that will happen in the meanwhile. We must do anything and everything we can to reduce that trauma, and that includes lowering posted speed limits.
5. There is evidence from around the world that when speed limits in a city are lowered wholesale, both the rate and severity of crashes also decreases. By as much as we want? No, but to reject this change out of hand for ideological reasons is, in my mind, a huge mistake.
6. There will always be egregious violators, drivers who drive as fast as they can no matter what. I think these drivers are actually responsible for most crashes. If these drivers can be caught and punished (removal of driving privilege and confiscation of vehicle) by any sort of enforcement, that is great. Redesigning a roadway does not eliminate these drivers or reduce their speed, it just makes it more likely that they will kill themselves along with the other people they are killing. That is small consolation.

I am absolutely in favor of roadways designed to self-enforce lower speeds. I have supported and helped design projects to do exactly that. And at no time have I ever felt that was enough. I think we need to use every action at our disposal (except biased traffic enforcement) to lower speeds. Now, not at some time in the future.