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Problem

Cut-through traffic that did not obey stop signs and traveled at unsafe speeds jeopardized local residents on a neighborhood street in Brooklyn.

Background

Residents of Brooklyn’s Prospect Park South neighborhood had long complained of drivers using their streets to avoid congested arterials. In 1996, the New York City Department of Transportation (NYC DOT) began a comprehensive speed hump program, using mostly flat-topped speed tables at mid-block locations. In 1997, Slocum Place, in Prospect Park South, was identified as a location needing traffic calming and a disincentive for cut-through traffic. Slocum Place was chosen because it was one of the few entries into the neighborhood and one of the most used cut-through routes.

Slocum had 75 vehicles per hour at peak times, and an estimated 750 ADT. Stratford Road, one of its cross streets, had 150 vehicles at the peak hour and an estimated 1500 ADT. Both roads were classified as local and had a 48 km/h (30 mi/h) posted speed limit.

A site visit to investigate placement of a NYC DOT-standard speed table on Slocum Place, revealed problems with installing speed tables at mid-block locations, including shortness of the blocks, closely spaced utility openings, driveways, and stop signs. Yet, the intersection of Slocum Place and Stratford Road presented an opportunity for a creative traffic calming measure, especially because it lacked the typical utility openings common to most city street intersections.

Solution

The intersection of Slocum Place and Stratford Road is all-way stop controlled, but the community perceived the stop signs to be often ignored. It did not meet warrants for a signal, so a speed table was installed in the middle of the intersection creating a de facto raised intersection.

The raised intersection at Slocum Place and Stratford Road followed similar contours of other speed tables in the city, 102 mm (4 in) high with 1.5 m (5 ft) long ramps. Instead of tapering the sides and offsetting them from the curb, all four sides have ramps. This ensures that a vehicle cannot avoid the hump by driving in the crosswalk, yet even a turning vehicle must have one set of wheels on the hump to round the corner. Furthermore, because curbs were not affected, drainage was not an issue.

Because the standard speed table could not be used, it became a test case for a raised intersection. Its success has shown that innovative traffic calming devices can be tested within existing policy and liability constraints.

Results

A post-improvement survey was conducted in 1997. It showed that 89 percent drivers stopped at the stop line after the raised intersection was installed, as opposed to only 64 percent before the improvement for a 25 percent increase. Additionally the number of peak hour vehicles decreased from a combined 227 for both streets to 152 after for a 33 percent reduction, showing this route to be less attractive as a cut-through.

In terms of pedestrian safety, drivers in the habit of obeying stop signs are more apt to yield to pedestrians. More importantly, the raised intersection physically forces all drivers to moderate their speed. Even the 11 percent of drivers that ignored the stop line had to slow down in the intersection area or risk a serious jolt to car and driver. Because the incidence of death or serious injury as a result of being hit by a vehicle decreases exponentially as speed is reduced, we infer that the slow vehicle speeds the raised intersection requires, greatly reduces the potential for serious injury to pedestrians at and near this intersection.

Contacts

Michael King, Architect
Traffic Calmer
126 Second Street
Brooklyn, NY 11231
Phone: (718) 625-4121
E-mail: miking@trafficcalmer.com

Ms. Randy Wade, Director
New York City Department of Transportation Pedestrian Projects
40 Worth Street
New York, NY 10013
Phone: (212) 442-7686
E-mail: rwade@dot.nyc.gov

NYC DOT Pedestrian Projects Web: www.nyc.gov/html/dot/html/get_around/ped/pedest.html

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