The Trouble with Speed Limits

Important news out of the Traffic Commission: at its meeting this past week, the body voted unanimously to recommend to City Council that the default speed limit on thickly settled city streets be reduced to 25 miles per hour. This mandate would apply only on streets with no existing speed limit signage. This prospect led to a lot of discussion at the meeting on how this rule would be enforced on city streets. While there is now a dedicated traffic detail at the Pittsfield Police Department, it would be logistically impossible to patrol every unmarked street in Pittsfield.

I have come to notice the fallacy with speed limit enforcement in cities, and it comes down to the nature of driving itself. People outside of cars want speed limits, people inside of cars do not. We all accept the unspoken truth that speed limit signs are a suggestion. The average motorist will drive at a speed that feels safe to them when uninhibited, or at whatever speed at which the platoon of traffic is flowing at the time. Some drivers may make the conscious choice to stay at or below the speed limit, but they are few and far between, myself included sometimes. (Though I am making a concerted effort to change that on my monthly or so car trips).

So why do we need speed limits? This is not meant to say that drivers should go as fast as they want, but rather, much as how some doors need to say "Push" and "Pull," why do we need to be instructed on how to use this device that is so commonplace: the city street? I believe the answer comes down to three factors in American urban design: Hierarchical street layouts, "forgiving" street design, and the problem of use separation and spatial mismatch.

Hierarchical street design. In an attempt to make cities more orderly for traffic engineers in the early twentieth century, roads and streets began be categorized in hierarchies, based on their "function." Up until then, the "function" of streets was quite simple: move people. There was never a concern about gridlock, volume to capacity ratio, speed limits, lane counts, clear zones, or signal timing until cars came along. Now, in order to better serve the flow of traffic (not movement of people), roads were categorized into how they would serve drivers. The basic categories of the hierarchy were local streets, collector streets, and arterials. The hierarchy is based on how many cars the street can move at a time. This is not an inherently bad system in itself, but the problem comes when the lines between the categories become blurred. In older cities like Pittsfield, the lines between these categories are more blurred than in newer Sunbelt and southwestern American cities. When a street changes but a neighborhood does not, the street's functional category may no longer match its surroundings. This usually happened in old cities during urban renewal times when existing streets were reclassified, but the surrounding context stayed the same. The reverse happened in new cities, where empty streets were later developed on, and turned into dangerous "stroads." In both cases, there is a mismatch between uses, which usually leads to a mismatch in the car speeds at which drivers feel comfortable and speeds at which neighbors feel comfortable.

Can you spot the Local, Collector, and Arterial streets in Cape Coral, Florida?

Can you spot the Local, Collector, and Arterial streets in Cape Coral, Florida?

Can you spot the Local, Collectors, and Arterials in Pittsfield?

Can you spot the Local, Collectors, and Arterials in Pittsfield?

Forgiving street design. When the speed limit on a road rises, there is more "clear zone" built into the road's design to account for driver errors. These errors could be distraction, misjudging a curve, failing to check blind spots, and more. This "forgiveness" in design usually comes in the form of wider travel lanes and wider shoulders on the sides of the road, as well as "clear zones" where trees, poles, and buildings are removed to lessen the chance that a driver crashes into something. These safety factors are indeed important on our interstates and rural highways, especially if they are unlit at night. On the flip side, these designs can turn into more of a hazard when they are introduced into urban streets and non-limited-access roads. On streets with inappropriately wide lanes and shoulders, drivers will be lulled into a sense that they can safely drive faster than the posted speed limit. While it may seem counter-intuitive to remove this extra buffer space in the name of safety, this course of action will accomplish far more than posting a speed limit sign ever would. Reducing marked lane widths down to ten or eleven feet will cause cars to pass each other more closely, making drivers pay extra attention and tap the brake more often. The farther apart drivers are from each other, the faster they will feel invited to drive.

Does anyone actually drive 25 miles per hour here? This same road design can be found in downtown Pittsfield or rural upstate New York.

Does anyone actually drive 25 miles per hour here? This same road design can be found in downtown Pittsfield or rural upstate New York.

Use separation/spatial mismatch. Finally, there is one more factor that affects driver speed which isn't necessarily related to road design. This idea has been built into the fabric of American city planning for a century now, and to the living generations of Americans, it just feels like it has always been there. That idea is the separation of land uses, which takes form in zoning. When zoning goes wrong, however, the burden that workers feel in long commutes or trips to the store can lead to faster and more aggressive driving. I have heard several complaints regarding lowering the city speed limit based on the idea that it will take even longer to get across town than it does now. Why do Americans regularly need to cross town to accomplish the tasks they have? The spatial mismatch that occurs from aggressive separation of land uses forms a vicious circle of car dependence and further separation of our land uses: residential, shopping, industrial, healthcare, agriculture, etc. The vast separation of the destinations we want to visit inherently makes us want to get there as fast as possible, and so we are poised to speed when we drive.


What course of action will solve the epidemic of speeding? I'm afraid that it is a problem as old as the Model T. The 25-mph law approved by the traffic commission will accomplish nil on its own. Advocates will often point to the Three E's for answers: Education, Engineering, Enforcement. We do our best to teach the rules of the road in drivers' education, but once class is dismissed, the only teachers will be social cues and fellow drivers, who may not always provide a great example. Engineering is beginning to transition to better designs for city streets and urban roads, with the acceptance of traffic calming infrastructure like speed humps, chicanes, roundabouts, bulbouts and safer crosswalks. Enforcement can only issue so many traffic tickets, and not everyone will be caught. One passive solution is the speed camera, though they can prove to be controversial in some communities. The biggest and most daunting issue not covered by the Three E's is the structural problem of the designs of our cities themselves. The best way to prevent speeding is not to drive in the first place. If we can bring our favorite and most important land uses closer together, and make our neighborhoods more human scaled, then the need for us to drive so frequently will wane. And if we do need to drive, then we will be more predisposed to do it safely and with regard to the space around us. Next time you climb into the car, and find yourself creeping above the speed limit, remember the system that you are currently part of, and consider setting an example on how to make it better. Then, drive like you mean it.

The PittsfielderComment