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Problem

Residents felt it was unsafe to cross a city street in their neighborhood and requested a mid-block signal and crosswalk. An engineering study showed that existing signal warrants could not be met to justify the signal.

Background

In 1997, the Penn South Co-op Board, on the upper West side of Manhattan, requested a mid-block signal and crosswalk on West 24th Street to improve the safety of pedestrians crossing the street destined for a playground in one direction or a subway station in the other. New York City’s Department of Transportation (NYC DOT) found that the crossing location did not meet warrants for a signalized, mid-block crossing. However, observational studies and neighborhood testimony confirmed that a significant number of crossings were made at the location of interest and along the entire block.

The Penn South housing development is characterized by towers set back from the street in park-like superblocks. To create the superblocks, West 24th and West 28th Streets between Eighth and Ninth Avenues were widened to 15 m (50 ft), as opposed to the normal 9.2 m (30 ft). The posted speed limit on West 24th (classified as a local road) was 48 km/h (30 mi/h) and weekday ADT was 5450 vehicles. The street’s extraordinary width meant more lanes and more capacity, but actual vehicle volumes were similar to unwidened streets in the neighborhood. The result: drivers drove faster.

On West 24th Street two heavily traversed mid-block passages intersect—one leads to the Penn South playground, the other to a subway station. In addition, other pedestrians take advantage of the bend in the road to shave time off their journeys. Taken together—wider road, faster cars, reduced visibility due to the bend, mid-block passages and desire lines, and multiple crossing points proved the location was ripe for intervention.

A year prior, NYC DOT had begun a comprehensive speed hump program. In a three-year period, about 300 humps were installed, mostly at mid-block locations using a flat-top design (a speed table). DOT planners looked to the traffic calming program for a solution that could be applied to a mid-block location.

Solution

A flat-top speed hump was proposed for 24th Street, and the project was recognized as a test case for a raised mid-block crossing. NYC DOT’s acceptance of the speed table design enabled creation of a de facto mid-block crosswalk, without formally and legally creating a crosswalk at a mid-block location. The concept design was presented to the Penn South Coop Board and they approved the proposal.

The speed table is 102 mm (4 in) high and 9.2 m (30 ft) long with 1.5 m (5 ft) ramps. By locating it where the two mid-block passages meet, drivers would be slowed at the point where most people cross the street and at all hours of the day and night. By not establishing a formal crosswalk, other pedestrians would still be free to cross the 240 m (800 ft) long street according to their desire lines. By using a speed table, which is wider than a normal crosswalk, the two opposing mid-block passageways could be connected, even though they did not line up exactly as a perpendicular intersection; and the pedestrian inclination to cross on a diagonal line would be accommodated by the table’s generous length.

Additionally, the street was narrowed at the crossing point to reduce pedestrian exposure. And to increase visibility, “No Parking” zones were established before the crossing. Flexible bollards were installed to reinforce the parking regulations.

The project cost was approximately $5500, including planning, design and construction, and was funded through the CMAQ program (federal ISTEA/TEA-21 funds earmarked for congestion relief and pollution reduction).

Results

A post construction study was conducted. Comparing prior speeds measured along the street with speeds taken at the speed table, showed mean speeds and maximum speeds were reduced by 43 percent. Speed at the crossing point fell 40 percent, between the 85th Percentile Speed of 53.1 km/h (33 mi/h) for the entire street with the 85th Percentile Speed at the new speed table of 32.2 km/h (20 mi/h). A person hit by a vehicle traveling 53.1 km/h (33 mi/h) has an 80 percent likelihood of death or serious injury, while 32.2 km/h (20 mi/h), the likelihood drops to 35 percent. By this measure, one can infer that pedestrian safety more than doubled at the West 24th Street raised-crossing.

The 85th percentile speed along the entire street was reduced by 15 percent, improving pedestrian safety even beyond the bounds of the improvement. Speeds for the entire street in the after condition were calculated by averaging the low speeds at the hump with the high speed elsewhere on the block.

The project successfully demonstrated the effectiveness of the treatment to improve pedestrian safety, as well as proving that innovative traffic calming devices can be tested within existing policy and liability constraints.

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

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