Northwood News ♦ February 2009

Traffic Calming 101 ... Plus a Pop Quiz!

By Linda S. Perlman

Are you confused about the recent “pedestrian safety” redesign of Arcola Avenue in Kemp Mill? Do you know the difference between speed humps and raised crosswalks? Do median or pedestrian “refuge islands” refer to immigration policy? Can you lose weight on a “road diet”? [Unfortunately, no: a “road diet” actually refers to a reduction in traffic lanes.]

“Traffic calming” involves street designs and traffic rules that slow and reduce traffic while encouraging pedestrians and bicyclists to share streets. The goals of traffic calming are to reduce traffic accidents, improve safety and convenience for pedestrians, give more space for children to play, eliminate noise and pollution, revitalize neighborhoods, and reduce crime. Here is a statement from the Institute of Transportation Engineers about the goals of traffic calming:

Traffic calming is the combination of mainly physical measures that reduce the negative effects of motor vehicle use, alter driver behavior, and improve conditions for non-motorized street users.

Speeding and unsafe driving on residential streets endanger the safety and livability of our neighborhoods. Successful traffic calming programs incorporate the three components necessary to slow down or reduce speeding and unsafe driving, namely: (traffic) Engineering, (community) Education, and (police) Enforcement. These are referred to by traffic engineers as the three “E’s” of traffic calming.

How is traffic calming done? Traffic calming is mainly visual changes to streets intended to bring about more attentive driving, reduced speeds, fewer crashes, and increased tendency to yield to pedestrians. Some of these visual changes include speed humps, traffic circles or roundabouts, sidewalk extensions, use of trees next to the street, and on-street parking.

Why not just install traffic lights and stop signs? According to traffic engineers, traffic lights and stop signs control traffic flow, but do not function as speed controls or pedestrian safety devices. Why not? Because, say the experts, drivers will simply speed up to make it through a traffic light and ignore stop signs.

Test Your Own Knowlege of Traffic Calming

Match the numbered items with the lettered definitions. Answers are below.

1. Speed humps	a. Raised circular islands placed in the center of an intersection.
2. Roundabouts (traffic circles)	b. Streets can be narrowed by extending sidewalks, adding planters or bollards, or adding a bike lane or parking. Narrowing the street gives drivers the feeling of being in a crowded area and makes slower speeds seem more natural to drivers.
3. Curb extensions (also called bulbouts)	c. Flat top speed humps at a crosswalk location. Used to slow vehicles, as well as indicate to drivers that special care must be taken at the intersection or crosswalk for pedestrian safety.
4. Narrower traffic lanes	d. Effective 1 October 2008, this became the Maryland state exercise. Get out of your car and try it!
5. Pedestrian islands	e. These narrow the width of the road by widening the street at the sidewalk or grass strip area and at pedestrian crossings.
6. Raised intersections or crosswalks	f. Parabolic or flat-topped raised pavement devices. These are typically spaced approximately every 500 to 750 feet. In Montgomery County, humps are generally only placed on residential streets with speed limits of 25–30 mph. Humps are less aggressive than speed bumps and are generally designed to allow snow plows and larger vehicles — such as school buses and fire trucks — to go over them easily.
7. Walking	g. Small raised islands or medians placed in the middle of a street. Such islands reduce the crossing distance for pedestrians, slow vehicle speeds, and give pedestrians a refuge area in the middle of a wide street.