Sent August 4, 2003

Safer Curbs and Ramps

A loyal CXLT called recently about a fall case at the entrance to a commercial building. I discussed several aspects of the design of parking lots, walkways and building entrances based on my ten years' design experience in the restaurant industry, mentioning that many details significantly affecting pedestrian safety are omitted altogether from building codes, and that the famous ADAAG accessibility guidelines are not primarily safety-related.

I mentioned to the caller the best treatment I knew of on this subject is my 1989 Slips, Trips and Falls book. The content is still current as far as the safe walking features are concerned, though the section on slipmeters is dated. During our conversation I was reminded of my past suggestions for inclusion of these guidelines in the original F1637 standard. The chairman of the task group never told me why this section on curbs and ramps was dropped altogether before the standard was balloted, but here are the suggestions I offered in March of 1993.

Curb Construction
Curbs should be smooth and flat, as part of the sidewalk surface, and they should be constructed in such a way as to minimize heaving or settlement that could leave vertical discontinuities in the walking surface. The top edge should be coplanar with the walking surface, and it should have an approximately square terminus with the vertical face of the curb.

Commentary: Construction methods (such as monolithic pour or doweling of adjoining slabs) should be employed to reduce the possibility of heaving or settlement.

Curved or rolled curb forms that present an indistinct edge (as in some extruded curb shapes) present confusing visual cues to the step-down line and may cause footing instability to the elderly and mobility-impaired.

Curb Height
Curb height should be six inches.

Commentary: Because most curbs in the US have traditionally been constructed to a height of six inches, there is a population expectancy that curbs will be that high. A curb of greater or lesser height presents a surprise that is often not detected visually until a trip occurs, since pedestrians do not normally examine walking surfaces closely, unless there is some obvious visual cue in their peripheral vision that attracts their attention. Of course, curbs higher than six inches present a greater injury potential, particularly to the elderly, because of the added distance of the drop.

Visual Factors
Curbs in pedestrian walkways should not be painted.

Commentary: Painting any walkway surface can produce slipperiness, especially when wet. A white concrete curb adjacent to a black asphalt pavement provides sufficient contrast to be an adequate visual cue to the change in elevation presented by the curb.

Ramps
The use of ramps should be avoided to the extent possible by designing facilities without unnecessary level changes. Where ramps are unavoidable, an attempt should be made to accommodate wheelchair traffic without unnecessary exposure of pedestrians to ramps.

Commentary: By locating designated handicap parking spaces to the opposite side of an entrance from the primary pedestrian traffic way, the mobility-impaired may be accommodated without exposing the vast majority of pedestrians to the confusion of ramp edges. [Ramps are inherently hazardous to pedestrians. They are not easy to walk on.]

Ramp Surfaces
Ramp surfaces should be flat without dishing or curving up of the edges.

Commentary: With a maximum curb height of six inches, there is no reason for curbing or dishing of ramp edges to accommodate wheelchairs. The presence of these unnecessary obstructions will cause pedestrians to slip or trip.

Ramp Edges
The maximum slope of any ramp should be 1:12.

Commentary: The ADAAG allowance of 1:10 of side flares on curb ramps is excessively steep and such configurations cause slips and trips of pedestrians. Curb ramps are inherently hazardous and should be avoided to the extent possible. A better arrangement is to locate the ramp at the end of a sidewalk so that the walking surface just slopes downward at 1:12. Ramp surfaces should not be painted. Painting makes them excessively slippery when wet, and painted surfaces become a continual maintenance problem.

Other Comments on STF
Although it is 12 years old, and production quality is not great, there is rich content in Slips, Trips and Falls based on actual fall accident investigation. The recommendations in the book were demonstrated effective by a steadily declining accident rate over the term that I worked for Marriott Restaurant Operations. The section on slipmeters is obsolete, but the design guidelines are still good, and there are many tips there you won't find anywhere else in print. There are a lot of before-and-after pictures as well as good and bad comparisons.

Hanrow Press is not easy to buy from, but I know people are still able to obtain the book, with enough persistence. I only get the usual author's commission of 15% on sales, so if you buy one it won't help me much, but maybe it would help your mother avoid a broken hip. As is mentioned on http://www.englishxl.com/pub.html, Pedestrian Slip Resistance is about slipmeters and slipperiness. Slip, Trips and Falls is about other fall hazards. You need both books.

Revisions to F1637
The original purpose of F1637 on Practice for Safe Walking Surfaces was to provide guidelines for construction and maintenance of facilities to make them reasonably safe for walking. This was important because (1) the A117 and ADA guidelines are only concerned with factors making facilities accessible to people having certain disabilities. Their writers have told me that these standards are not safety codes, and they are not interested in modifying them to make facilities safer for people who are not handicapped. Therefore, it was felt needful for F13 on Pedestrian and Walkway Safety and Footwear to write a standard specifying details affecting pedestrian safety.

F1637 is a very important standard that should be protected from evisceration by its adversaries, and it should be beefed up in the areas of curbs and ramps to cover these serious slip and trip hazards. There are members of F13 who make a living defending negligent design in court who have opposed F1637 since its passage, and they will attempt to weaken it further, if they can't prevent its renewal. Others in F13 with no safety engineering background have opposed F1637 simply because their intuition didn't tell them the things that accident analysis has told the safety engineers writing F1637. Those of you who are inclined toward making the world safer for walking should work actively with us to protect what we have in place and further strengthen it by adding important specifications for walkways, curbs and ramps. Don't fail to vote with us when changes are balloted.

See some information about this and other pedestrian-related safety standards on http://www.englishxl.com/stds.htm.

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Bill@EnglishXL.com
William English, Inc.
Phone 239/728-3254, FAX 239/728-2304.
Visit http://www.EnglishXL.com for the latest in Slip Resistance Technology.

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Copyright 2003 William English. This page may be forwarded freely if not altered in any way, but reproduction without the written permission of William English is prohibited


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