Jay Grossman P.E.
October 11, 2002
I am concerned about two of the proposed changes, first concerning crosswalks:
Limiting the crosswalk cross slope to 2% at intersections, and hence the
roadway's profile grade to that same level, will significantly increase the cost
of infrastructure improvements. Even here in flat Indiana, it is not unusual to
have profile grades over 2% through an intersection. I would suggest that 5%
(1:20) is a better number, consistent with current maximum grades on major
As pedestrian accessible routes at mid-block are apparently all right with a
cross slope that matches the road profile grade, whatever it may be, perhaps a
more tempered approach to cross slopes at intersections is appropriate.
The grading required to flatten out an intersection will be extensive as
vertical curvature requirements for roads don't allow for abrupt changes. Using
Indiana design standards, at a 35 mph design speed typical in urban areas,
flattening a 5% slope out to 2% at an intersection will require reconstruction
of 180 feet up slope of the intersection and 110 feet down slope, plus the width
of the intersection itself. A simple intersection improvement would, in this
example, become a vastly more complicated and costly undertaking involving
grading, drainage, and road reconstruction. This added cost may well delay many
improvement projects, and any accessibility improvements that might have been
included in a simpler project would also be delayed.
My second concern is with roundabouts. First, the requirement for a barrier on
the street side of the sidewalk seems unfounded. In lengthy reading on
roundabouts in other countries, who have 30 or more years of experience using
them, providing a physical barrier for detectability was never mentioned as
having been a safety concern. As a detectable pattern at ground level is
sufficient at a crosswalk or train station platform, why is the edge of a
roundabout any more dangerous? Traffic in a roundabout generally circulates at
15 mph, much less than the 35-40 mph of traffic rushing for a green light at a
If a pedestrian steps over a curb into a roundabout, there is a much better
chance that motorists will have a chance to stop or swerve than when a
pedestrian steps into a crosswalk at a signal just as the light changes and a
motorist is speeding to make the light. Furthermore, the accident data I have
seen has never shown any instances of accidents involving pedestrians
inadvertently straying into the circulatory roadway. Is it prudent to protect
against a type of accident that has never occurred?
Finally, the requirement for pedestrian activated signals at roundabout
crossings also seems extreme. As stated before, traffic at roundabouts is going
much slower than that at signals on a green phase, and the accident data reflect
how these lower speeds affect safety. Watching a video of a roundabout at
Michigan State University shows how, with 5000 pedestrian crossings a day,
roundabout crosswalks are generally safer than those at signals. When a
pedestrian steps into the crosswalk traffic has time, and does, slow to allow
them to cross. Observing roundabouts in Colorado showed the same yielding to
pedestrians in the crosswalks by traffic.
A colleague participated in a visual impairment understanding exercise at a
roundabout in Wisconsin. Blindfolded and with a cane, after a couple of tries
with a guide, he was able to learn to listen for traffic and safely cross the
roundabout approaches without aid. If a person blindfolded for less than half an
hour can learn to cross safely at roundabouts, is it unreasonable to think those
with permanent disabilities can learn to do the same?
Thank you for the opportunity to comment,
Jay Grossman P.E.