Leading Pedestrian Interval –
A Solution We’ve Been
Waiting For!
by Dona
Sauerburger, COMS
with input from
Michael King
March 1999
newsletter
Metropolitan
Washington Orientation and Mobility Association (WOMA)
All pedestrians who cross in the crosswalk
during the green light have problems with drivers who turn into their path and
refuse to yield to them. These drivers,
who are disobeying the law, have been the cause of many pedestrian injuries and
deaths, and they are one of the main concerns of blind people who are afraid to
cross streets independently.
Now, there is a possible solution that
reduces the danger for all pedestrians, called the leading pedestrian interval
(LPI).
The LPI provides a few seconds head start
to the pedestrians. The pedestrian
signal comes on while the signal for the drivers remains red; after pedestrians
have had a chance to start their crossing, the drivers get their green signal.
Fortunately, engineers in our area are
starting to use LPIs. I noticed LPIs at
intersections in Washington, DC over a year ago, and several months ago I
noticed one for pedestrians crossing Wayne Street at Colesville Road in Silver
Spring, Maryland.
LPI
-- how it can work for blind people:
It is difficult or impossible for blind
people to recognize when the intersection they are crossing has an LPI for them
unless the intersection also has accessible pedestrian signals. For example, several weeks ago I talked with
two blind people who have crossed Wayne Street at Colesville for years. They hadn’t realized that the timing of the
cycle had been changed and that the pedestrians were given a head start
there. They thought that the
pedestrians had become “brave” because so many of them started their crossing
before the light changed to green.
Even when blind people realize there is a
LPI, it is difficult for them to use it without an accessible pedestrian
signal. I explained the LPI to my
client who wanted to cross Wayne, but he was never able to recognize when the
pedestrian signal came on until the traffic on Colesville had started. By then, it was too late to start his
crossing because of the aggressive right-turning drivers (the reason for
installing the LPI there!).
However, if the signal can be provided
with accessible pedestrian signals, blind people can take advantage of the LPI
as well as sighted pedestrians, and reduce the danger and fear of crossing.
The rest of this article is excerpted
from a paper, listserv messages, and report by Michael R. King on traffic
calming devices installed at intersections in New York City. Michael is an architect and the former
Director of Traffic Calming for the New York City Department of Transportation
(NYC‑DOT) [NOTE written February, 2006: Michael King is currently with Nelson\Nygaard at 121
West 27 St, Suite 705, New York NY 10001-6207, phone 212.242.2490; His e-mail address is miking@trafficcalmer.com or mking@nelsonnygaard.com].
Michael will deliver his paper at the
Urban Street Symposium in Dallas in June, 1999, and he graciously allowed us an
advanced reading. This information can
hopefully have a powerful positive influence on those who design our
intersections, and may be useful to help us advocate for changes.
Do LPIs increase safety?
by Michael R. King
The “pedestrian head start” is a sexier
name for the leading pedestrian interval (LPI) or a delayed vehicle green. [”Pedestrian head start” is a play on
words, as the “pedestrian head” is the pedestrian signal.] Simply put, with an LPI, the WALK signal
turns on 3 to 10 seconds before the vehicle green. This allows pedestrians to establish their presence in the
crosswalk ahead of turning vehicles.
The result is that drivers yield to pedestrians, instead of intimidating
them by turning quickly.
LPIs have been used in New York City for
at least 20 years. The NYC‑DOT
has installed 55 LPIs at various intersections since 1975.
Recently we analyzed data and found that
the LPI reduced the [crash rate between pedestrians and turning vehicles] by
12%. Relative to control sites, the
rate fell 28%.1 Factored
by severity, the relative rate fell 64% [see explanation in footnote #2].
Other studies have found similar results, and as a result, New York City is
installing more LPIs, especially at locations of high turning movements.
In terms of potential safety benefits, we
know that 35% of the 14,000 vehicle/pedestrian crashes in New York City every
year involve turning vehicles. If the
LPI truly reduces this number by 12%, then 600 vehicle/pedestrian crashes per
year would be prevented.
These numbers are impressive, and
considering that 2 out of every 3 people hit in crosswalks in New York City are
hit while crossing with the signal, this bodes well for the future of
the LPI as a tool to reduce pedestrian/vehicle crashes in New York City. Overall, we found that LPIs had the greatest
effect on intersections with high turning movements, regardless of pedestrian
traffic.
NYC‑DOT uses LPIs of 6‑10
seconds. Richard Retting of the
Insurance Institute for Highway Safety has studied LPIs with 3 second intervals
and found similar results. [Ed. See below – article from WOMA newsletter
9/97.]
Analysis
of Pedestrian/Vehicular Crashes at Leading Pedestrian Intervals in New York
City
(adapted
from August ‘98 NYC‑DOT report)
by
Michael King
Methodology
To understand how the LPI affects
pedestrian safety, we analyzed fourteen locations with recently installed LPIs
and substantial crash data. We obtained
up to ten years’ worth of crash data where possible (five years “before” and
five “after”). From this data, we were
able to note vehicle action, pedestrian action, and the severity of the
crash. The severity factor allows one
to assign a numerical value based on cost to the public (ambulances, police,
road repair, etc.) and then rate each crash accordingly.2 In order to assess the relative difference
in crash rates, we collected data at the surrounding intersections. We also determined the statistical relevance
of crashes at each site.
The basic analysis compares
“before”/”after” data at the intersection to the “before”/”after” data at the
control site. This allows us to isolate
the rate of change in crashes that would be affected by the installation of a
LPI. These types of crashes include:
1. Total:
all reported crashes involving a vehicle;
2. Crashes
with an injured person(s);
3. Crashes due to driver
error, such as failure to yield right-of-way, inattention, disregard for
traffic control, turning improperly, etc.;
4. Crashes where a
vehicle hits a pedestrian(s) in the crosswalk;
5. Crashes involving the
pedestrian crossing with the signal;
6. Crashes involving
vehicles turning left or right.
Theoretically
the installation of an LPI will help to prevent and/or minimize all of the
above crashes, especially types 3, 4 & 5.
However, the LPI has a direct influence on type 6 -- those involving
turning vehicles. We therefore used the
statistics for this type of crash in assessing the performance of the LPI.
Findings:
Averaged together and compared to the control
sites, the LPIs at the fourteen intersections yielded a 28% relative decrease
in “turning” crashes, with a relative severity decrease of 64%.
In absolute terms [not comparing it to
control intersections], the LPI reduced the rate of crashes involving turning
vehicles by 12%, with a 55% drop in severity.1
While the severity of crashes involving an
injury rose 15%, and the difference in the rates of all reported crashes and
crashes involving injuries was unchanged, the crash rates for the three other
types of crashes affected by the LPI all fell from 27% to 88%.
Of the Manhattan locations with a
significant decrease in LPI crashes, four have easily identifiable vehicle
characteristics:
At East 14 Street, both University Place and
Union Square West are one‑way into 14 Street. Therefore all vehicles must turn.
East 20 Street at First Avenue is the only
through street between 14 and 23 Streets.
Therefore most drivers wishing to access the intermediate blocks must
turn at this intersection.
On East 62 Street, drivers wishing to access
the Queensboro Bridge must turn onto 2 Avenue.
Especially in the PM peak hours, this movement is quite heavy.
Vehicles traveling on East 96 Street to the
97 Street Central Park traverse must make a right turn on Madison Avenue, and
then a left at East 97 Street.
Conclusions
The data shows that Leading Pedestrian
Intervals have a positive effect on pedestrian safety, especially where there
is a heavy concentration of turning vehicles.
We surmise that this effect occurs regardless of pedestrian volume.
Discussion
There are about 11,000 traffic signals in
New York City, about 85% have pedestrian indicators. A program to establish LPIs at all of these intersections would
undoubtedly be a large undertaking. In
that many of the signals are manually controlled, it would require breaking out
and reconfiguring the cam. On the other
hand, installing LPIs citywide, accompanied by a public outreach and education
campaign, may save in the long run as fewer “wait for green” signs would be
required, and the laws regarding yielding to pedestrians in the crosswalk would
be accentuated from an engineering standpoint.
If taking 6 to 10 seconds from the green
time has negative impacts on vehicle volume and level of service, one can trade
the LPI seconds for increased steady DON’T WALK time at the end of the green
phase. On streets that are 30‑60 feet wide, the pedestrian (walking at 3
feet per second plus start up time) needs 15‑25 seconds to cross. Given a typical 90 second cycle with 45
second phases, this allows for 20‑30 seconds of time that can be
dedicated solely to the driver. [A “phase” is the time in which one group or
groups of drivers and pedestrians have their turn to cross the intersection; a
“cycle” is the time in which everyone at the intersection gets the green signal
once.].
1.
Michael explained that crashes at intersections with LPIs fell an average of
almost 12%, but during that same time period, crashes at the control sites increased
almost 17%. Assuming that the crashes
at the experimental intersections would also have increased 17% if they hadn’t
had LPIs, this means a reduction of 28% crashes (the difference between ‑12
and +17 is rounded out to 28).
2.
Michael explained that crashes are factored in New York state by severity,
based on the cost to society. The
following factors that were used to rate the crashes were provided by New
York’s Department of Transportation:
Collisions with fatalities were
multiplied by 2729, those whose victims were hospitalized and seriously injured
were multiplied by 1214, those whose victims were hospitalized but not
seriously injured were multiplied by 303, and those whose victims were injured
but walked away were multiplied by 76.
The total was then divided by the number of crashes.
The benefit in factoring crashes is that,
while the number of crashes may not change much when an LPI is installed, if
they are less severe, then overall we can judge that the location is safer. In other words, it would be preferable to
have 20 people with cuts and broken bones than 2 dead pedestrians.
In this case, even though the number of
crashes was reduced by only 12% with
LPIs, the severity of the crashes was reduced by 55%.
Traffic Signal Adjustment May Make Street Crossing Safer
by Dona
Sauerburger, COMS
September 1997
newsletter
Metropolitan
Washington Orientation and Mobility Association (WOMA)
Many of our students have great
difficulty crossing streets at intersections with traffic signals where there
is frequent, heavy traffic turning into their path when the signal is green for
them. The drivers often do not yield,
and a number of visually impaired travelers in our area have been hit in these
situations. Many of our students are
understandably reluctant to cross at places like these, and some intersections
are virtually impossible for blind people to cross because of this problem.
According to a publication of the
Insurance Institute for Highway Safety that was written in the June 1997 “TRB
Pedestrian Digest” (“Field Evaluation of a Leading Pedestrian Interval Signal
Phase at Three Urban Intersections”), about 37 percent of pedestrian injury
crashes and 20 percent of fatal crashes occur at intersections. It states that many conventional
countermeasures try to address this problem by either encouraging pedestrians
to notice potential “conflicts” with vehicles, or by encouraging drivers to
yield to pedestrians. However, it will
come as no surprise to most of us O&Mers that they report that “public
education and enforcement campaigns have generally not produced tangible and
long-lasting safety benefits.”
Thus, a study was done to examine the
influence of a three-second leading pedestrian interval (LPI). The LPI provides a brief, exclusive signal
phase dedicated to pedestrians just before the traffic in the parallel street
get their turn.
The result was that the use of a
three-second LPI “reduced conflicts between pedestrians and turning vehicles,
reduced the incidence of pedestrians yielding the right-of-way to turning
vehicles, and appeared to make crossing the street somewhat easier.”
For additional information, contact the
Insurance Institute for Highway Safety, 1005 N. Glebe Road, Arlington, VA
22201-4751 (703-247-1500).