Lane Narrowing & Lane Removal
Lane narrowings remove excess width from existing traffic lanes without changing the number of lanes. Lane removals, also known as "road diets," reassign underused traffic lanes to other functions. These design techniques, while not traffic calming devices, have powerful traffic calming benefits. Both may be accomplished by adding markings, turning lanes, pedestrian safety islands, expanded pedestrian space, on-street or separated bike lanes, parking, or other functions.
Raised Speed Reducer
A raised area of a roadway that deflects both the wheels and frame of a traversing vehicle with the purpose of reducing vehicle speeds. The two basic types of raised speed reducers are speed humps and speed cushions. Both are typically raised 3 to 4 inches above the level of the roadway, and both have a proven speed-reducing track record in New York City. While speed humps span the width of the street, a speed cushion is divided into narrow segments, so that vehicles with wider wheel bases (buses, emergency vehicles, large trucks) are not affected.
Gateway
A combination of traffic calming and visual measures used at the entrance to a low-speed street to slow entering vehicles and discourage through traffic. Useful at all roadway transitions to slower-speed environments, gateways are especially suited to entrances to residential side streets and Shared Streets. The design elements of a gateway can include Curb Extensions, a Raised Crosswalk or driveway treatment, a Raised Median, landscaping or trees, and community facilities such as seating and public art.
Raised Crosswalk
A marked pedestrian crosswalk at an intersection or a mid-block location constructed at a higher elevation than the adjacent roadway. A raised crosswalk is essentially a speed table that meets the adjacent curbs, and has a full-width crosswalk contained within the flat portion of the table, usually 10- to 15-feet wide. It combines the benefits of a Raised Speed Reducer with increased accessibility and enhanced visibility for the pedestrians crossing.
Raised Intersection
An entire intersection raised above the level of the surrounding roadways. The intersection is typically raised to sidewalk height.
Chicane
A series of narrowings or Curb Extensions that alternate from one side of the street to the other forming S-shaped curves to slow traffic. Chicanes discourage or make it impossible for drivers to drive in a straight line. This can reduce vehicular speeds.
Neighborhood Traffic Circle
A round traffic island in the center of a traditional intersection. Primarily applicable to lower-traffic intersections as a horizontal speed reduction method for through traffic.
Roundabout
An intersection with circular, one-way (counter-clockwise) traffic around a central circle in which entering traffic yields to traffic already in the roundabout. Roundabouts can vary in size (diameter) and number of lanes and can be modified with signalized crosswalks. Roundabouts are distinguished from “old-style” traffic circles/rotaries by their rules for yielding on entry and key design features targeting low design speeds.