Minding the 2% rule: The best ways to measure sidewalk cross slopes
Question: What is the "official" way to measure a cross slope on a sidewalk to ensure it complies with the ADA’s 2% or less rule? Should this 2% be measured over the entire width (from the back of the walk to the face of the walk)? Also, should the 2% be measured at 1-foot segments or at 2-foot segments of the sidewalk cross slope? — Scott, Tennessee
: Scott, a great question. My answer is twofold:
- It is best to measure from the back of the walk to the face. Since the most recent Public Right of Way Accessibility Guidelines (PROW) require a 4-foot-wide sidewalk, I suggest using a 4-foot-long ruler or at least a 36-inch-long digital measurement ruler as your measuring tool.
- There are no specific guidelines as to using 1-foot segments versus 2-foot segments. However, the more measurements the better.
Put your digital ruler on wheels
My friend Mike Ross is an engineer in the street maintenance division of the City of Overland Park, Kan. He and his staff developed a simple, wheeled device in which you can insert a digital ruler and then roll the device along the sidewalk for readings without constantly bending over and picking up the ruler and putting it down again. It is important to advance a short distance and then stop so an accurate reading is possible. The actual digital readout, of course, faces the person pushing the device.
This tool will also help with measuring the slope of curb ramps, linear slopes of ramps, trail slopes, etc. Most digital rulers also allow you to remove the actual measuring tool in the middle of the ruler to measure small areas.
You can easily make your own version of this tool. When I was working on another project with engineering firm HDR Inc. in Kansas City, Mo., my HDR colleagues saw the tool and were inspired to create their own. If you inspect the pictures of both the Overland Park Public Works and HDR tools included in this article, you’ll see that the way the ruler is inserted is slightly different, but both do a wonderful job.
Mike was kind enough to give me one and I use it all the time.
Take care and best wishes to each of you trying to do your best to improve the world we use and to fulfill the lives of everyone!
This digital survey ruler was placed on wheels by City of Overland Park,
Kan., Public Works Department employees.
After seeing how Overland Park’s device worked, HDR Inc. employees made
their own rolling measurement tool.