Sunday, April 22, 2012

ADA Curb Ramps


By: Maeve Ragusin

A curb ramp, by definition, is the sloped transition between sidewalk and street level, with usage geared towards pedestrians, cyclists, with heavy emphasis placed on wheelchair users.  With origins dating back to post World War II, curb ramps were initially designed with disabled veterans in mind.  Due to their subsequent popularity among disability rights activists, the curb ramp can now be widely found in most all urban areas.

At their inception, curb ramps were considered voluntary additions, however in 1990 the Americans with Disabilities Act passed.  It mandated that curb ramps be available on all sidewalks.  Since then, there has been an explosion of newly built curb ramps, especially in urban areas.  There are various types of curb ramps, and strict specifications they must meet.


Types:



Standard Curb Ramps: the overall incline of the ramp must be less than 8.33% and 4’ wide, with a 2% cross slope at both the bottom and top landings.  There must be a 4X4’ top landing area (2% by 2%) for clearance.  To create a bottom landing at gutter level and prevent wheelchair users from tipping backwards, the slope from the outer gutter coming into the curb ramp must be less than 5%. 



 The example curb ramp, to the right, can be found in near campus, at the intersection of Fenway and Forsyth St.

There are, in most cases, two 45° wings, which start at the top of the curb ramp.  Engineers aim to design the slope along the wing of the ramp to be 2%, so that the ramp is accessible if approached from the side.  The majority of all curb ramps fall within this classification.  There is typically a 2'X3’ panel of detectable surface tiles, widely referred to as domes, responsible for tactile warning.

Apex Curb Ramp: these ramps follow the same design specifications as standard ramps.  Rather than serving one crosswalk however, which requires two ramps per return, an apex ramp is center facing and serves both crosswalks at the intersection.  While being simpler in the design and construction phases, these ramps can compromise safety, as they require users to be more exposed to traffic.

 The example curb ramp, above, can be found in Jamaica Plain at the intersection of Green St and Lamartine St.

Returned Curb: this type of ramp is virtually identical to a standard ramp, with the noted absence of wings; this option is preferred only if there is not space for wings to be built or if the area surrounding the ramp is unpaved.  The example ramp shown below is surrounded by grass, making a returned curb a better option. A small curb is built around the ramp in this scenario, starting flush with the sidewalk at the top landing, and matching the existing curb at the base of the ramp. 

Two good examples of this are the midblock ramp on St Stephen St and on the northwest corner of Huntington and Parker Ave.  In the case of Huntington and Parker St, designers chose to increase the width of the ramp (in this case 8’ wide instead of the standard 4’), and eschew wings all together.  While unconventional, since this design does not detrimentally impact accessibility, it’s a valid design.



















The St Stephen St ramp on the other hand is poorly designed.  Firstly, there is adequate space for wings or a wider ramp; there is no reason for the returned curb.  Secondly and most importantly, the ramp itself is not 4’ wide because designers did not consider the width of the surrounding curbs, each at about 6” wide.  In reality, only 3’ of this ramp are usable, and therefore not accessible by ADA standards.





Longitudinal Ramps: These designs are typically used only if the width of the sidewalk does not allow for a top landing.  In this scenario, there are actually two ramps, which lead to a landing from which pedestrians cross.  In principle, this type of curb ramp still meets the traditional specifications.  Both ramps must have a slope of less than an 8.33% slope, with a 2% cross slope at the top and bottom, and landing must be a 4’X4’ 2% landing.  The panel of domes is place on the landing here.  This is an innovative design that maintains accessibility despite strict space restraints.

 

All in all, increased awareness about disability outreach has prompted many municipalities to build ADA curb ramps.  They benefit the overall population and are as a whole, well liked for ease of use and accessibility.  Older curb ramps may need to be updated to achieve the current ADA specifications and I believe that soon, every street corner in every major city will be equipped with curb ramps.



1 comment:

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