Public Comment - Additional Materials submitted by public at meetingUS Department of Transportation
3.11 Speed Cushion
DESCRIPTION AND GENERAL PURPOSE
--:So\\ Y\. ~c.(,\-c ,-~
'vv\7, re-lo ~ ~n+-
q / lq/tt,~
A speed cushion consists of two or more raised areas placed laterally across a roadway
(see Figure 3.11.1 ). The height and length of the raised areas are comparable to the
dimensions of a speed hump. The primary difference is that a speed cushion has gaps
(often referred to as "cutouts") between the raised areas to enable a vehicle with a
wide track (e.g., a large emergency vehicle, some trucks, some buses) to pass though
the feature without any vertical deflection.
Another difference between a speed cushion and a speed hump is the common
practice for the top of the speed cushion to be level. Like a speed hump, the profile of a
speed cushion is gentle enough to provide a comfortable ride when traversed at a
speed of approximately 20 to 25 MPH.
[A speed cushion is also known as a speed lump, speed slot, and speed pillow.]
The cutouts in the speed cushions are positioned such that a passenger vehicle cannot
pass it without traveling over a portion of the raised pavement.
A speed cushion is often a preferred alternative to a speed hump on a primary
emergency response route or on a transit route with frequent service.
[Two field studies of three speed cushions measured reductions between 5 and 7 mph for
85th percentile speeds (Source: FHWA, Engineering Speed Management Countermeasures: A
Desktop Reference of Potential Effectiveness in Reducing Speed, July
2014) https:llwww.highways.dot.gov/safetylspeed-managementlengineering-speed-
management-countermeasures l
Figure 3.11.1. Speed Cushion with Passage that Straddles Centerline
(Source: Jeff Gulden)
APPROPRIATE APPLICATION
Appropriate Application -Speed Cushion
Type of Street
Intersection or
Roadway
Segment
Roadway
Cross-Section
Generally appropriate for both local and collector streets
Placed at a midblock location; as an example, Pennsylvania recommends a
distance of 150 feet from an unsignalized intersection and 250 feet from a
signalized intersection
Should not be placed on a sharp curve; ITE Guidelines for the Design and
Application of Speed Humps recommends a minimum horizontal curve radius
of 300 feet
Can be used on a single-lane one-way or two-lane two-way street (examples
are shown in Figures 3.11.2 and 3.11.3)
Typically installed with an urban cross-section (i.e., curb and gutter)12