Slow down…with all the speed bumps!

Posted by on Sep 9, 2014 in Blog Article | No Comments

Speed bumps, speed humps, speed pillows, speed tables…whatever name they go by, they’re popping up all over Chicago! As a resident of a healthy Chicago neighborhood, it’s easy to see how their use has become, to say the least, rampant.
Before I discuss my observations on this topic, I want to offer a few notes regarding this blog posting:

  • The point of this article is NOT to dispute the applicability of whether or not speed bumps/humps/pillows/tables is justified from a technical standpoint. Rather, it is simply to present one resident’s experiences now that they are becoming commonplace throughout Chicago.
  • Technically, speed bumps, humps, pillows, and tables are all slightly different and have varying applications. For the purposes of this article, I’m lumping them all together as techniques used to slow on-street traffic through changes in pavement elevation.
  • Speed bumps have their inherent pros (ability to slow traffic, low installation cost, etc.) and cons (potential vehicular damage, difficulty for plowing and street cleaning, impact on emergency responsiveness, etc.). Again, the point of this article is NOT to dispute rather or not they should be used, but rather to point out curiosities about how they’ve been applied from the perspective of a resident.

Neighborhood Context

The typical residential block in Chicago is 600’ long by 300’ wide, with an alley that runs parallel to the long dimension. Generally, neighborhoods utilize alleys for garage access and have on-street parking lining the block. While some streets remain two-way (especially those on ¼-mile spacing), several local streets are one-way. As a result, the general condition is to have a residential street with a curb-to-curb dimension of about 30’ with one traffic land and two on-street parking lanes. This combination (no on-street curb cuts, one-way traffic, and relatively wide traffic lanes (usually about 14’) has led to instances of motorists travelling faster than appropriate for the residential density and level of pedestrian activity in most neighborhoods. In 2012, the City of Chicago unveiled its Pedestrian Plan that identifies a number of potential solutions for traffic calming. The traffic-calming toolbox is comprehensive, with speed bumps, humps, and tables included, but also identifying neighborhood traffic circles, alignment offsets, bumpouts, and other techniques for calming traffic and enhancing pedestrian safety. Since the adoption of the Pedestrian Plan, speed bumps, humps and tables have popped up all over the city, likely due to their low cost related to other types of improvements. In most cases, speed bumps are installed in response to a petition submitted by residents to the local Alderman.

Curiosity #1: Must they be so frequent?

In many cases, such as the instance shown on the illustration below, speed bumps are located so close together that they reduce the vehicle to idle speed. As a test, I tried to see how fast I could go after crossing the first speed bump before having to rapidly slow down for the second one. (The speed bumps are located approximately 150’ apart.) The result…15 MPH! Keep in mind, that’s gunning it with the intent of going faster than most cars would. While the intent is certainly to force vehicles to travel at a safe speed, the spacing of the speed bumps seems excessively close together.

HLABlog-Speed Bumps


Curiosity #2: Why are they located so close to signed intersections?

Most of Chicago’s residential street intersections are controlled by 4-way stop signs. Despite the spacing of stop signs every 600’ or 300’, some speed bumps are located extremely close to intersections. In the illustration below, the speed bump is approximately 100’ – that’s length of 5 parking spaces – away from an intersection controlled by a stop sign. The dimension of the block and the stop sign preclude drivers from travelling too fast, yet there is a speed bump located where motorists would be slowing down anyway.

HLABlog-Speed Bumps


Curiosity #3: Must they be designed to do damage to a vehicle?

Speed bumps get people to slow down because motorists don’t want to damage their vehicles. But they shouldn’t be designed to cause damage when the motorist behaves properly. There are several speed bumps – especially in Chicago’s alleys – that are so drastic that they cause jarring movements even when crossed at idle speed. This application demonstrates the fact that, in many cases, their application is not in-line with the intent.

To reiterate, I’m not suggesting that the City of Chicago and other communities abandon the use of speed bumps. I am a firm believer that pedestrian safety should be the priority, especially in urban areas that support transit ridership, local commercial districts, and neighborhood schools and amenities. Rather, I’m suggesting that it is important for planners, engineers, elected officials, and others to assess a problem and develop appropriate solutions that actually address the issue at hand. In my opinion, the use of speed bumps in Chicago has become a low-cost solution to a problem that a) may or may not exist, and 2) may call for a different solution.

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