Bicycle Railing Height Report - AASHTO - Subcommittee on Design

DETERMINATION OF APPROPRIATE RAILING HEIGHTS FOR BICYCLISTS
NCHRP 20-7 (168)
Chapter 6 - Findings and Recommendations
In the absence of scientific study, empirical data, and actual or simulated crash data, the
first <strong>AASHTO</strong> guideline for the height of a bicycle railing was based solely on the theory
that a railing should be equal to or higher than a bicyclist’s center of gravity (COG) to
prevent the bicyclist from vaulting or falling over the railing. In the absence of a
thorough analysis of the height of the COG of a bicyclist, the difference in height of the
COG of a pedestrian and a person on a bicycle was estimated. A conservative estimate of
an additional 12 inches was applied to the 1.1-meter (42-inch) pedestrian railing height,
and a 1.4-meter (54-inch) high bicycle railing height was established.
No other considerations or variables have been applied to the prevailing theory that the
COG must be lower than the railing to prevent falling over the railing. For instance, the
lateral force necessary to rotate the bicyclist’s COG over the railing has not been
considered in the height of the railing. The speeds of the bicyclist, direction of travel,
and angle of collision with the railing have also not been considered.
Crash records are few and inconclusive. In the only reported crash involving a fall over a
1.4-meter (54-inch) railing, the bicyclist was traveling at a high rate of speed, and
collided with the railing at an angle.
The survey and outreach process revealed a sense of insecurity regarding a 1.1-meter (42-
inch) railing height. This is especially true for tall bicyclists crossing long bridges with
high winds.
A real concern also exists regarding the obstruction of views associated with high
railings. This concern has, in some cases, resulted in the reduction of railing height after
the railing was installed.
Finally, survey respondents identified cost as a concern, especially when compared with
the linear cost of a separate shared-use path.
It is reasonable to conclude that the “one size fits all” approach to bicycle railing design
is not adequate. In many locations, especially along shared-use paths at the top of slopes
in a scenic corridor, the theoretical additional degree of safety afforded to bicyclists by a
1.4-meter (54-inch) high railing would not likely offset the associated aesthetic and cost
impacts. However, locations exist, especially on high, wind-prone bridges or on high
speed curves, where a higher railing would lend a greater degree of comfort to a bicyclist,
and could prevent a bicyclist from vaulting over a railing as a result of a high speed crash.
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