Thursday, April 22, 2010

Speed Humps and Chicanes on Walnut Street, Brookline

Submitted by Zhi Li, (Jeff)

Walnut Street is a two-way, one-lane local street. It parallels the Boylston Street, and it is about 1 mile long between Warren Street and high Street. Walnut Street passes through the residence area and it connects the Brookline Reservoir Park to the Boylston Street.

The target user in Walnut Street should be residents. So safety is the most important thing in this road. The travel lane seems narrow is about 9 ft wide, and some area with one side parallel parking spaces. There are sidewalks which are 5 ft wide on each side of the street. Because this street passed through the residence area, so there are houses on each side of the street, and they are not far beyond the road.

The objective design of this road should be control vehicles speed to a low level for pedestrians’ safety. There are some traffic calming in this road, they are two speed humps and one chicane.

The chicane is on about 100 ft back from the Walnut Street – High Street intersection. Sometimes it is successful to reduce the vehicle which just entering this road with the narrow travel lane when there was an opposite vehicle. However, there are some problems in this design. Firstly, there is not a sign to show drivers there is a chicane ahead. Secondly, the radius of the chicane line seems like small, because vehicles have to slow down a lot or let’s say they almost stop if they do not want to beyond the double yellow real lines. More importantly, when the car wants to restart from a very low speed or let’s say from stop, it will make more noise. So it is not considerate to the people who live in those houses which are near the chicane. Finally, this street’s traffic volume is not high, it is hard to see two cars meet each other in this chicane at the same time. So vehicles always go beyond the double yellow real lines, just as the picture shows. And they do not slow their speed as well.

There are two speed humps in Walnut Street, one is on the Walnut Path – Walnut St intersection, the other speed hump is on Oakland Rd – Walnut St intersection. There is a sign before about 50 ft away from the speed hump, and it makes drivers to pay attention that there is a speed hump ahead. In addition, there are several horizontal lines which show how long the driver will reach the speed hump. Moreover, the sign also recommends the speed which vehicles pass through the speed hump, the recommendation speed is 20 mph. And those two speed humps in Walnut Street are also as crosswalks for pedestrians. Basically, the speed hump in Walnut Street is very effective to reduce the speed of vehicles, because the speed humps’ height is about 5 inches, that is to say the speed hump is as tall as the curb. So vehicles have to slow down a lot to cross those two speed humps in this street if drivers want to feel comfortable. The speed which drivers always pass through the speed hump is less than 20 mph usually, it is about 10 mph.

There are still some problems on speed humps in this street, although they can reduce the vehicles’ speed a lot. Initially, those speed humps’ height is too high, the common height of a speed hump is 3 or 3.5 inches usually. So it is not comfortable for drivers when they pass through those two speed humps. Furthermore, as the above said, they have to slow down a lot for pass through the speed hump comfortably, and when they restart the vehicle, it will make more noise especially the truck than when they passed a lower speed hump. Most importantly, as the picture shows, the house is very near the road, so it is not considerate to the residents. Last but not least, the pavement is not clear enough, it is fading, so drivers hard to see a speed hump ahead if they did not see the sign before the speed hump.

To sum up, the traffic calming design in Walnut Street paid more attention to the major target that is to reduce the speed of vehicles for pedestrian’s safety, and the traffic calming in this street is very effective to control the speed of vehicle as well. However, there are some minor problems made this road design is not good enough. For example, the chicane’s radius is a little small and there is not a sign to awake drivers there is a chicane ahead, and the speed hump is too high that may made vehicles slow down a lot so that they will make more noise to restart.


  1. The analysis of the chicane is confused -- either it makes cars stop (causing some noise) or it doesn't work to slow cars down; can't be both.

    Did you notice the chicane or speed hump causing noise? Is this a legitimate complaint, or just something made up to oppose traffic calming?

    The spacing between humps is important, but wasn't reported.

  2. Also -- while speed when crossing the hump is important, speed between humps is the more important measure of effectiveness.

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