There actually is a provision for edge protection found in the ADAAG. Although
it pertains specifically to landings, in the absence of any other guidance, I
think the courts would consider it the best available. It provides that edge
protection is required for a drop-off greater than half an inch if the drop-off
is within ten inches of the minimum dimension of the feature. If the public
agency involved has selected the ADAAG as its PROW standards then the minimum
width for a sidewalk would be 36 inches so any drop-off greater than half an
inch that was in an area where the sidewalk width was 46 inches or less would
require edge protection; if they are using the PROWAG then the width would be
58 inches or less. In addition, its not just ADA that applies here; there is
always the doctrine of standard industry practice that is applied by the
courts. There are many industry publications on the design of pedestrian
facilites and States are beginning to adopt what I like to call walkside design
criteria (I am currently putting together Nevada's version). The states of
Washington and California, among others, have such criteria in place already.
I think your best approach would be to discuss this matter with the person in
charge of risk management for the public agency involved and point out that
although there may not be specific regulatory requirements for edge drop-off
protection for sidewalks, engineers and public works officials have a legal
responsibility to provide safe designs in accordance with current standard
industry practices.

FDOT uses the following for Pedestrians...(PPM Chapter 8.8)
"There are two cases that require shielding. As shown in Figure 8.2 (Case I), a
drop-off greater than 10 inches that is closer than 2 feet from the
pedestrians' or bicyclists' pathway or edge of sidewalk should be considered a
hazard and shielded. Also, as shown in Figure 8.2 (Case II), a slope steeper
than 1:2 that begins closer than 2 feet from the pedestrians'or bicyclists'
pathway or edge of sidewalk should be considered a hazard and shielded
when the total drop-off is greater than 30 inches. Also, depending on the depth
of the dropoff and severity of the conditions below, shielding may be necessary
for cases other than described above."

As always, engineering judgement is key to this analysis and resolution.

I have seen Florida's guidelines and was interested in knowing if there are any
National Guidelines from which Florida based its recommendations. We are
involved in a project where is a 24 inch vertical drop-off between the back of
the sidewalk and a parking lot. Building codes indicated that anything less
than 30 inches does not require a railing. Without a railing, our condition
does not seem to be safe.

The drop-off criteria found in Florida's Design Standards is not an
accessibility issue, but a safety one. It is intended to protect pedestrians
from a relatively minor hazard. The 24" cited in the standard is a horizontal
measurement: is there a drop-off hazard within 24" from the edge of the
sidewalk? If the hazard is within 24" we protect users with a 2-pipe
'guiderail.' This would prevent someone from stepping off the sidewalk and
stumbling/rolling down a steep slope (>1:2) or fall over an embankment. The
intent of the 24" is to also allow someone who inadvertently steps off the
sidewalk to have recovery room to get back onto the sidewalk, without the need
for a railing. These are used to protect the hazard (guardrail) and not as an
accessibility aid (handrail.)

The vertical drop of 24 inches is immediately behind the sidewalk. We have room
to provide a handrail and short retaining wall. The location is a corner of an
intersection heavily traveled by trucks. My concern is someone standing at the
corner waiting to cross as a WB-50 or 67 is making the turn. The pedestrian may
have a tendency to back-up and fall down the drop.

I was hoping to find some type of national guideline to support my concern and
take to our client.

You pose an interesting question that I don't believe is adequately addressed
by the current ADAAG, Nevada and Florida's guidance notwithstanding. Because
the question of when and where ped handrail should be used, Elizabeth Hilton,
TxDOT, and I submitted a problem statement for research to the NCHRP.
Unfortunately, I do not know the status of the problem statement and whether it
will be funded.

Some of the questions that arise have to do with should handrail be required if
the edge of the sidewalk is within a certain distance of an embankment? Does
the embankment height make a difference? Does the embankment slope make a
difference? What about the horizontal offset from the edge of sidewalk to the
slope? Should handrail be provided for all sidewalks with a longitudinal grade
greater than some value so people in non-motorized wheelchairs can pull
themselves up the sidewalk?

Loads of questions...few answers. Support the research...contact Elizabeth
Hilton or me.