Architectural and
Transportation Barriers Compliance Board
Draft Guidelines for Accessible Public Rights-of-Way
In response to the Draft Guidelines for Accessible Public Rights-of-Way (June
17, 2002) proposed by the Architectural and Transportation Barriers Compliance
Board (Access Board, 2002), the Insurance Institute for Highway Safety opposes
the provisions that would mandate installation of traffic signals on pedestrian
crosswalks at all roundabouts.
Background
Modern roundabouts are designed to function safely and efficiently without
traffic signals and, in most cases, are constructed to replace less safe and
less efficient stop sign-controlled intersections. Roundabouts are circular
intersections with specific design and traffic control features that eliminate
the need for traffic signals. These features include yield control of all
entering traffic, channelized approaches with raised splitter islands, and
geometric curvature to ensure slow travel speeds for vehicles entering into and
within the roundabout.
Roundabouts are relatively new in the United States. Las Vegas, Nevada, built
the first modern U.S. roundabout in 1990 (Jacquemart, 1998), and since then only
200-300 roundabouts have been constructed nationwide. In comparison, Australia
and many European countries have been installing roundabouts extensively for
decades, with, for example, more than 2000 roundabouts built in the Australian
state of Victoria alone.
Effects on road safety of converting intersections to roundabouts has been the
subject of extensive research in the United States and abroad. Results clearly
indicate that roundabouts are an extremely safe form of intersection traffic
control. For example, an Institute-supported evaluation of 23 U.S. intersections
converted from stop sign or traffic signal control reported large reductions in
motor vehicle crashes after roundabouts were installed (Persaud et al., 2001).
Overall, crashes were reduced by an estimated 40 percent, injury
crashes declined by 80 percent, and crashes resulting in fatal or
incapacitating injuries were reduced by 90 percent. A recent meta-
analysis of 28 separate roundabout safety evaluations from outside the United
States concluded that roundabouts were associated with a 30-50 percent reduction
in the number of injury crashes and a 50-70 percent reduction in fatal crashes (Elvik,
in press).
Although these studies do not provide conclusive evidence of the safety of
pedestrians at roundabouts (primarily because of small samples of pedestrian
crashes), available research suggests roundabouts can provide a relatively high
degree of safety compared with intersections with stop sign and traffic signal
control. For example, in the Persaud et al. (2001) study, four pedestrian
crashes were reported during the before period and one was reported during the
period after roundabouts were built (this difference was not significant due to
the small sample size). Brude and Larsson (2000) analyzed pedestrian crash data
at 72 roundabouts in Sweden and concluded that roundabouts pose no problems for
pedestrians compared with conventional signal control intersections. For
single-lane roundabouts, the observed numbers of pedestrian crashes were 3-4
times lower than for comparable signalized intersections, controlling for
pedestrian volumes and traffic flow. Jordan (1985) examined pedestrian crash
patterns at roundabouts in Victoria, Australia for the 4-year period 1980-83. A
total of 35 pedestrian crashes were reported (average 9 crashes per year) at
approximately 800 roundabouts. The author characterized this as an extremely low
rate of pedestrian crashes and concluded that “concern for pedestrian safety at
roundabouts, while well intentioned, is unfounded.” Tumber (1997) conducted a
review of pedestrian safety at roundabouts, also in Australia. The study focused
on roundabouts constructed on arterial roads within the Melbourne metropolitan
area during 1987-94. During this period, 64 pedestrian crashes were reported at
approximately 400 roundabouts, for an average crash rate of 0.02 crashes per
roundabout per year. The severity of pedestrian crashes (as indicated by the
proportion of injuries classified as either serious or fatal) also was lower for
roundabouts than for intersections with other forms of traffic control.
The safety of blind pedestrians at roundabouts has been questioned by some
advocates of the visually impaired, but direct evaluations of crash data are not
available. In an indirect evaluation of the issue, Guth et al. (2002) collected
data regarding the ability of blind pedestrians to use their hearing to
distinguish “crossable” gaps in traffic at roundabouts from gaps that were
considered by the authors too short to afford a safe crossing. This work was
supported by the Access Board. Three study sites in Maryland included a
low-volume, single-lane roundabout; a large, urban, high-volume, two-lane
roundabout; and an urban, intermediate-volume, two-lane roundabout. Six blind
and four sighted pedestrians observed traffic at roundabout crosswalks and
indicated by pressing a button whenever they believed they could complete a
crossing before the arrival of the next vehicle. For the low-volume, single-lane
roundabout, gaps between vehicles longer than 10 seconds were very common.
Pedestrians observed frequent periods of “all quiet” and concluded that
listening for such periods appeared to be “an effective strategy for identifying
acceptable gaps.” In addition, “risky” judgments (ones where there would not
have been sufficient time to reach the splitter island before the arrival of the
next vehicle) were few and not significantly different across the two groups
(blind and sighted pedestrians). For the two high-volume, two-lane roundabouts,
the average duration of the gaps between vehicles was about 6 seconds, and most
gaps were judged too brief to allow pedestrians to fully cross before the next
vehicle arrived at the crosswalk. Also at these two roundabouts, blind
pedestrians were more than twice as likely as sighted pedestrians to indicate
there was an acceptable gap when approaching vehicles were
2-3 seconds away.
Despite the finding by Guth et al. (2002) that blind pedestrians can adequately
judge gaps at single-lane roundabouts with little difficulty and as well as
sighted individuals, the Access Board is proposing guidelines that would require
signalization of pedestrian crosswalks at all roundabouts on the basis that the
safety of blind pedestrians mandates such devices. This proposed requirement
would apply even in rural settings where pedestrian activity is infrequent and
where blind pedestrians may be nonexistent. However, traffic signals appear to
be unnecessary at single-lane roundabouts and, if mandated, actually could be
detrimental to highway safety. It is likely that the arbitrary addition of
traffic signals to well designed roundabouts could increase the risk of injury
crashes due to disruptions in traffic flow. Also, substantial costs associated
with installation and maintenance of traffic signals might discourage some
communities from constructing roundabouts. Even for high-volume, two-lane
roundabouts, the Guth et al. field study does not make a compelling case for
traffic signals because of weaknesses in the research methodology. Blind
pedestrians were driven to roundabouts and then observed after minimal exposure
to these unfamiliar locations. This is unrealistic because blind pedestrians
typically do not wander into such areas without a guide to provide initial
orientation. Guth et al. merely provides evidence of the perception of risk, not
actual risk. The blind pedestrians may have been more willing to press a button
when they believed they could complete a crossing than to begin crossing, thus
inflating the numbers of “risky” judgments. Also, comparable data were not
collected for intersections controlled by traffic signals or stop signs.
Compared with conventional intersections, roundabouts can provide improved
access and safety for blind pedestrians as well as sighted individuals because
of specific roundabout design and operational characteristics. First and
foremost, traffic speeds within roundabouts are very low -- typically 15-20 mph
-- compared with considerably higher traffic speeds at most traffic signal and
stop sign-controlled intersections. Pedestrian refuge islands at roundabouts
provide for short crossing distances. Also, roundabouts are relatively simple
intersections that eliminate left turns, right turns, and the associated
turning-vehicle conflicts common at conventional intersections. By comparison,
conventional intersections are characterized by higher traffic speeds, longer
crossing distances, and are more complex due to two-way traffic flow and
frequent vehicle turning movements. Preusser et al. (2002) reported that 25
percent of motor vehicle-pedestrian collisions in Washington D.C. involve
turning vehicles.
The combination of low traffic speeds, short crossing distances, and absence of
turning vehicles in conjunction with White Cane Laws – laws in 47 states that
require drivers to yield the right-of-way to a person carrying a white cane or
accompanied by a guide dog --- provide safe crosswalks for blind pedestrian at
many roundabouts. Additional measures that could enhance safety include textured
pavement in conjunction with ramps to help lead blind pedestrians to crosswalks,
raised crosswalks that can further slow entering and exiting traffic, and
pedestrian yield signs in both directions of the crossing that require drivers
to stop for pedestrians waiting on the crosswalk. Also, specific training can be
developed and provided to help the visually impaired perceive gaps in traffic
and to give drivers cues to stop.
Signalizing roundabout crossings can be justified when the combined volumes of
pedestrians and vehicles are high or at locations with complex geometry such as
high-volume school zones. In Australia and Europe, the vast majority of
roundabouts are unsignalized, but some roundabouts in urban areas do have
pedestrian signals. The recommended threshold for signalizing pedestrian
crossings in the United Kingdom is:
PV2 > 1 108,
where
P = Pedestrian volumes per hour (average of peak 4 hours)
V = entering vehicles per hour (average of peak 4 hours)
Rather than adopting the Access Board’s recommendation to require signalization
on pedestrian crosswalks at all roundabouts, regardless of need or
justification, the Institute supports the Australian and European practice of
installing pedestrian signals at appropriate locations based on objective
criteria.
Opposition to Draft Guidelines
The Access Board indicates that the absence of stopped traffic presents a
problem for pedestrians with vision impairments in crossing streets. It is true
that traffic signals at conventional intersections establish a stop-and-go
pattern that can assist blind and visually impaired pedestrians in crossing busy
streets by producing audible cues about vehicle movements. However, a large
majority of U.S. intersections are not controlled by traffic signals. Most
intersections are governed by one-way or two-way stop sign control, which only
require vehicles traveling on minor intersection approaches to stop. At most
stop sign-controlled intersections, vehicles traveling on major intersection
approaches are not required to stop, and at such locations travel speeds often
can exceed 40-50 mph. So clearly, the absence of stopped traffic, while
potentially problematic for pedestrians with vision impairments, is a frequently
encountered condition. Like countless other crossings where traffic does not
stop, blind pedestrians primarily rely on hearing to identify gaps in traffic.
The draft guidelines also suggest that crossing at a roundabout requires a
pedestrian to visually select a safe gap between cars that may not stop. This
statement is inaccurate as well as insulting to pedestrians who are blind. With
proper training, blind pedestrians use their hearing to identify and select gaps
in traffic at a wide range of unsignalized crossings where traffic may not stop.
Even the Access Board-sponsored research by Guth et al. (2002) reported that
blind individuals can cross single-lane roundabouts with relatively little
difficulty and with few “risky” judgments (and more than half of U.S.
roundabouts are single-lane, as reported by Jacquemart (1998)).
The Access Board claims that people who are blind or visually impaired are
unable to make eye contact with drivers making it impossible to “claim the
intersection.” Blind pedestrians obviously are unable to make eye contact with
drivers, regardless of the type of intersection traffic control. However,
because roundabouts produce low travel speeds, short crossing distances, and
eliminate turning vehicles, pedestrian crossings at roundabouts should be safer
for blind pedestrians relative to many other unsignalized crossings. White Cane
Laws, which require drivers to yield the right-of-way, further enable blind
pedestrians to claim the intersection at roundabout crossings despite the
inability to make eye contact.
Summary
The Institute opposes provisions of the draft guidelines that would require
installation of traffic signals on pedestrian crosswalks at all roundabouts. The
Access Board has provided no scientific evidence in support of this proposed
requirement and, furthermore, it is likely that the arbitrary addition of
traffic signals to well-designed roundabouts could increase the risk of motor
vehicle crashes, in particular rear-end collisions, due to disruptions in
traffic flow. Substantial costs associated with installation and maintenance of
traffic signals might discourage some communities from constructing roundabouts
or installing pedestrian crossings. Compared with conventional intersections,
roundabout design and operational characteristics can provide improved access
and safety for blind as well as sighted pedestrians, and additional measures can
be taken to further improve the safety of blind pedestrians at unsignalized
roundabout crossings such as textured pavement, raised crosswalks (speed
tables), and increased lighting. Rather than adopting the Access Board’s
recommendation to mandate signalization on pedestrian crosswalks at all
roundabouts -- regardless of need or justification -- the Institute supports the
practice of installing pedestrian signals at appropriate locations where needed,
based on objective criteria.
Sincerely,
Richard A. Retting
Senior Transportation Engineer
References
Architectural and Transportation Barriers Compliance Board. 2002. Draft
guidelines for accessible public rights-of-way. Washington, DC. Available:
http://www.access-board.gov/rowdraft.htm#DRAFT.
Brude, U. and Larsson, J. 2000. What roundabout design provides the highest
possible safety? Nordic Road & Transport Research 12:17-21.
Elvik, R. 2002. Effects on road safety of converting intersections to
roundabouts: A review of evidence from non-US studies. Transportation Research
Record. Washington, DC: Transportation Research Board, in press.
Guth, D.; Long, R.; Ponchilla, P.; Ashmead, D.; and Wall, R. 2002. Non-visual
gap detection at roundabouts by pedestrians who are blind: a summary of the
Baltimore roundabouts study. Washington, DC. Available: http://www.access-board.gov/publications/roundabouts/
research-summary.htm.
Jacquemart, G. 1998. Modern roundabout practice in the United States. Synthesis
of Highway Practice 264. Washington, DC: Transportation Research Board.
Jordan, P.W. 1985 Pedestrians and cyclists at roundabouts. Proceedings of Local
Government Engineers Conference. Perth, Australia.
Persaud, B.N.; Retting, R.A.; Garder, P.E.; and Lord, D. 2001. Safety effects of
roundabout conversions in the United States: empirical Bayes observational
before-after study. Transportation Research Record 1751, 1-8. Washington, DC:
Transportation Research Board
Preusser, D.F.; Wells, J.K.; Williams, A.F.; and Weinstein, H.B. 2002.
Pedestrian crashes in Washington, DC and Baltimore. Accident Analysis and
Prevention 34:703-10
Tumber, C. 1997. Review of pedestrian safety at roundabouts. Victoria,
Australia: VicRoads, Road Safety Department.
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