Standardization is a goal always worthy of consideration. However, in some
situations, its disadvantages may outweigh its advantages. Such is the case when
setting traffic signal pedestrian clearance intervals. Please reconsider the
referenced report's "call" for calculating all pedestrian clearance intervals
nation-wide on the basis of an assumed 3.0 ft./sec. walking speed.
In Miami-Dade County, we have thousands of pedestrian clearance intervals at
thousands of traffic signals. All of their interval durations have been
calculated based on the speed of typical pedestrians using each crossing on a
case-by-case basis. Although we often use the "industry-standard" of 4.0
ft./sec., we equally often make whatever adjustments are warranted to best serve
the public at that particular intersection.
In downtown business districts where daytime traffic congestion is severe and
pedestrians are generally in a hurry, we increase the standard assumed crossing
speed to 4.5 ft./sec. Near retirement and assisted living facilities, we
decrease the standard assumed crossing speed to 2.5 ft./sec. In tourist zones
and in school zones, assumed crossing speeds between those two extremes are
used.
At locations where we use the 2.5 ft./sec. speed, changing to 3.0 ft./sec. would
be unsafe for disabled people with walkers and in wheelchairs.
On the other hand, decreasing the assumed speed to 3.0 ft./sec. at locations
where there is no regular demand for such would severely and unnecessarily
reduce the capacity of over a thousand intersections in Miami-Dade County alone.
Most of those intersections are already experiencing vehicular demand volumes in
excess of their capacity during one or more hours of the day. Decreasing their
capacity would immeasurably increase vehicular stops, delays, fuel consumption,
other operating costs, pollutant emission, wasted man-hours, driver frustration,
and rear-end collisions.
Therefore, for the benefit of all members of the public, disabled and fully
abled alike, I strongly recommend and request that the proposed nationwide
pedestrian crossing speed standard of 3.0 ft./sec. be eliminated from the
referenced document.
Thank you for offering this forum for the public to comment on your proposals.
In general, I find most of your report to be well thought out and well written
and commend you for this work. I generally support your goal to encourage all
jurisdictions to make reasonable efforts to accommodate all of our citizens.
Robert B. Williams, P.E., P.T.O.E.
Traffic Signal System & Operations Mgr.
Traffic Signals & Signs Division
Miami-Dade Public Works
index
next comment
