Subject: Pedestrian crossings at roundabouts
The report is NCHRP 672.
Does anyone know how we may access
the referenced UNC and MN DOT studies?
As for MW's comments, I believe my view is somewhat different. I hypothesize
that the lower yield rate at the exit compared to the entrance is not due to
roundabout geometry and speed as much as it may be due to selfishness of
drivers and in my view, an insufficiency in driving codes.
Here's my logic on the first point. The driver approaching the roundabout
entrance is (should be) slowing down and preparing to stop if needed. My
opinion is this makes the driver more accepting of yielding to a pedestrian
waiting at the road edge because the driver's thought could be: I may need
to stop anyway so why not be nice and let the pedestrian cross. A test of
this theory would include observations at roundabouts with different
geometries but also would consider the available sight distance to
conflicting vehicular traffic. My contention is the sight distance has much
more influence on the yield rate than does geometry. I believe a minimum
speed geometry roundabout with excessive sight distance will produce a lower
yield rate than would a higher than desirable speed geometry roundabout with
limited sight distance. If the driver can see that he/she will not have a
vehicle conflict before getting to the crosswalk, the 'me' attitude will
likely govern and the driver will not stop for the pedestrian. In this
selfish case, I would expect the yield rate at the entrance and exit to be
similar. As for yield rates at exits, I contend that the key again is the
attitude of the driver and not the speed itself. I would expect that with
other parameters equal, drivers will yield at exit crosswalks at similar
rates whether R3 speed is in the teens or above 30 (mph). I state 'other
parameters equal' because I expect the context is of primary importance.
Driver behavior in a ped dominant environment such as an urban commercial
district is going to be night and day different than one where the motor
vehicle is dominant, i.e. suburbia USA.
My second point addresses how the law (and enforcement) may be modified to
help the pedestrian. I believe most USA driving codes state that the driver
shall yield to a pedestrian in the crosswalk. In this case, no moving
violation will occur until the pedestrian risks life and limb and steps into
the street. I think this part of the driving code should be revised so that
the driver shall yield to a pedestrian WAITING to cross an unsignalized
crosswalk. With that law in place AND campaigns to educate/enforce it, I
would expect yield rates to be high regardless of the roundabout's geometry
or the crosswalk being at the entrance or exit. Connecting to another
important roundabout issue in the USA, if the aforementioned (utopia) were
achieved, would the Access Board move to delete signalization of multilane
crosswalks from the PROWAG?
Jay Vorisek, P.E.
CrossRoad Engineers, P.C.
(317)780-1555x126
Michael Wallwork
Sent: Tuesday, June 04, 2013 10:01 PM
To: ROUNDABOUTS@LISTSERV.KSU.EDU
Subject: Re: Ped & Bike safety at roundabouts
Speed control requires a designer to fully understand roundabout design,
speed control design vehicles requirements. NCHRP 272 shows that exit speeds
at radial design roundabouts, roundabouts where exit speed is controlled by
the exit radius is overall well below the exit speed at Offset left
roundabouts.
Two studies one by UNC and one done for the Minnesota DOFT show that yield
rates to pedestrians at the departure crosswalks decreases more so than on
the approaches due to vehicles speed, probably because vehicles are
accelerating on the exit rather than slowing on the approaches, Also, that
it only takes a few extra miles per hour to cut Yield rates from 83 to 43
percent.
Michael Wallwork, PE
Alternate Street Design, P.A.
904 710-2150
Comments (0)
You don't have permission to comment on this page.