How to Build an Accessible Curb Cut
Because this site gets a number of hits on accessibility specifications of actual curb cuts, I thought I would post a couple of resources for misguided visitors. Specifically I’ll outline the little that I’ve been able to find out about curb cuts and the Americans with Disabilities Act (ADA).
Definition
First off a definition from the Wikipedia entry on curb cuts:
A curb cut (US) or dropped kerb (UK) is a ramp leading smoothly down from a sidewalk to a street, rather than abruptly ending with a curb and dropping roughly 10-15 cm (4~6 inches).
Where
Page 4 of the official Checklist for Existing Facilities (PDF) from the US Department of Justice Americans with Disabilities Act Home Page asks the question, “Do curbs on the route have curb cuts at drives, parking and drop offs?” From this I’m going to posit that these are the three places where curb cuts are required.
Slope
The next paragraph in a discussion on ramps discusses the slope ration and states that “the slopes of ramps (be) no greater than 1:12,” it then goes on:
Slope is given as a ratio of the height to the length. 1:12 means for every 12 inches along the base of the ramp, the height increases one inch. For a 1:12 maximum slope, at at least one foot of ramp length is needed for each inch of height.
More Information
For those who are looking for more information, the US Department of Transportation Federal Highway Administration has a document entitled Designing Sidewalks and Trails for Access, including an entire chapter on “curb ramps” including information on how curb ramps impact different populations, different types, best practices and great diagrams.
If you’re looking for a basic checklist on facility accessibility, check out this Facilities Checklist from the National Center on Workforce and Disability.
The 1:12 ratio means that, if your curb is 6 inches high (which is typical) then your curb cut is 6 feet wide.
This makes the curb cut effectively the width of the entire sidewalk, which is how they are designed here in Moncton.
In the winder, however, these cuts freeze over and become slippery. And on an icy surface, even a slope of 1:12 is dangerous – it is common to slip on them and fall.
However, since the curb cut is the entire width of the sidewalk, there is no place for a pedestrian to find a flat surface onwhich to walk.
For this reason, I favour a smaller ratio – 1:6, say, which is still navigable by car or wheelchair, but which noneless offers a safe walking surface in icy weather.
You bring up an interesting and important point about curb cuts- in discussions on accessibility they are often highlighted as a prime example of Universal Design, how a modification for a specific population benefits everyone. However, as noted, curb cuts can also at times be an inconvenience. Besides the example noted above, curb cuts often facilitate easy entry of bicycles and rollerblades onto sidewalks- unwelcome guests for pedestrians.
Too often Universal Design is hailed as a perfect solution for everyone, which may be true only in rare, ideal situations. Captions are great in a number of different situations, but they bother some people. The point being that if a 6:1 ratio works for almost everyone and is significantly less of an inconvenience for everyone else then it should probably at least be considered. Regarding this specific example, I personally have no idea. Any idea what the slope ratio requirements in Canada Stephen?