Raised Intersection

Raised Intersection

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Article Overview

A raised intersection is a vertical traffic calming installation used to slow traffic through an intersection and place pedestrians and vehicles on the same plane. This provides a safety advantage for pedestrians, as it puts them on "equal footing" with vehicles.

Raised intersections are generally installed on residential or minor collector streets, and avoided on higher volume streets. The gentle ramps that lead to the heart of the intersection, and the large raised area, are designed to avoid damage to large vehicles and emergency response vehicles.

The raised intersection is a natural extension of the family of vertical traffic calming devices that includes speed bumps, humps, and cushions , as well as the speed table and raised crosswalk .

Reducing Cut-Through Traffic

In 1997, the New York City Department of Transportation installed a raised intersection on a residential street in Brooklyn in response to excessive cut-through traffic and frequently ignored stop signs. [1] A post-installation study showed that 89 percent of drivers stopped at the stop line after the raised intersection was installed, as opposed to only 64 percent prior to the installation, for a 25 percent improvement. Similarly, the number of peak hour vehicles decreased from a combined 227 for both streets to 152 afterwards, for a 33 percent reduction.

Traffic Calming Effectiveness

In addition to reducing cut-throughs, raised intersections can reduce average vehicle speed. An installation at Berkshire and Marcella Streets in Cambridge, MA (lower photo) resulted in a speed reduction (85th percentile speed) from 30 mph to 21 mph. [2] Other studies have revealed less dramatic speed reductions - only 1% average speed decrease at 3 sites [3], but it is unclear how far away from the intersections these measurements were made. Nevertheless, speed reduction to be expected from raised intersections is considered generally less than from speed humps and other shorter devices. [3] Effectiveness of any traffic calming device is highly situation-specific, making it difficult to generalize.