| Introduction |
| The City of Portland, Oregon has researched ways to
provide safe unsignalized crossings for pedestrians. A concept that has shown promise is
known as passive pedestrian detection which is defined as the detection of pedestrians in
a stationary or moving state at the curb-side of and/or in a pedestrian crossing by means
other than those requiring physical response by the pedestrian. |
| The City of Portland=s research
identified five types of sensor technologies that could be used to passively detect
pedestrians (Beckwith, 1998). The technologies include: passive infrared, ultrasonic,
microwave radar, video imaging, and piezometric. Of the five technologies three of the
sensor types (passive infrared, ultrasonic, and microwave radar) met initial performance,
maintenance, and cost requirements and were further tested. Of these, the passive infrared
sensor proved to be the most effective for the Portland area. |
| Since the Portland research, the City of Camas, Washington and the
Washington State Department of Transportation have shown interest in the use of passive
detection at unsignalized locations and have identified and designed a test site to use
this technology. The remainder of this report covers a brief background of the chosen test
site, the different crossing alternatives developed for the site, how the final crossing
design was chosen, and evaluation tests to be conducted at the site. |
| Background |
| In Camas, Washington, students from local neighborhoods must cross a
major state route (Everett Street (SR 500)) when traveling to and from school. Existing
average daily traffic (ADT) along Everett Street is 7,400 vehicles per day with an 85th
percentile speed of 32 to 34 mph. One of the main pedestrian routes (located at the
intersection of Everett Street/19th Avenue) crossing Everett Street shows a pedestrian
count of 82 pedestrians when school is in session. Most of the pedestrian crossings take
place the hour prior to the start and the hour after release of students from school. To
help increase the visibility and safety of this crossing, local agencies wanted a crossing
treatment such as a traffic signal or the use of other traffic calming techniques to help
pedestrians cross the facility. Gap studies along Everett Street showed that traffic
control was warranted only during the time children were traveling home from school in the
afternoons. |
| The City of Camas undertook an exhaustive public involvement process to
insure that needs of all parties that affected by the crossing treatment would be
addressed. The parties involved included the City of Camas, Washington State Department of
Transportation, local police and fire departments, the local school district, City
Council, and neighborhood citizens. |
| Crossing Alternatives |
| Four options were initially developed to provide traffic/pedestrian
control for the Everett Street crossing. A description of each option follows with a plan
view of each option attached at the end of this report. |
| Option 1: Flashing Beacons with Passive Infrared
Detection |
| This option proposes the use of passive infrared sensors to detect when
pedestrians are present at the landings of the crossing. Once the pedestrian is detected,
flashers (located in advance of the crossing and/or at the crossing) are activated to
alert motorists that pedestrians are at the crossing. These flashing beacons can be turned
off after a timer has timed out or if desired, infrared sensors can also be positioned to
monitor the crossing itself keeping the beacons activated as long as a pedestrian is in
the street. Once the pedestrian has crossed the street and left the landing area, the
beacons are deactivated until another pedestrian comes up to the crossing. |
| Passive infrared sensors allow for the supplemental warning devices to be
active only when a pedestrian is present at the crossing and does not rely on the
pedestrian to physically activate the system by the push of a button. This type of sensor
technology (rather than another sensor technology) was chosen for this option for the
following reasons: |
- Designed to operate at extended temperatures from -40o F to 120o
F.
|
- Weather conditions in the Camas area do not affect sensor operations.
|
- Maximum Range is 40 feet with a well defined detection zone..
|
|
|
- Effectiveness and detection rate (98 to 99 percent) proven through the Portland research
(Beckwith, 1998).
|
| In addition to the infrared detection, raised islands would be
constructed in the middle of NE Everett Street to provide a storage area for pedestrians
as they cross NE Everett Street and to constrict travel lanes for vehicles to encourage
low speeds through the crossing area (see attached). Curb cuts would be provided in the
median to allow bicycle and wheelchair access across the street, and to direct pedestrians
or bicyclists so they face in the direction of oncoming traffic before continuing across
the street. |
| Option 2: Traffic Signal Control with 19th
Avenue Westbound Only West of Everett Street |
| Option 2 proposes traffic signal control on NE Everett Street and NE 19th
Avenue. This option includes restricting the west leg of the intersection to in
(westbound) traffic only by constructing an modified curb extension. This proposed design
eliminates the need to signalize all four legs of the intersection, which would be
difficult due to the offset of NE 19th Avenue. The resulting T-intersection would be
signalized, the existing crosswalk on the north leg would be realigned to run
perpendicular to NE Everett Street, and crosswalks would be added to the east and south
legs of the intersection. |
| Option 3: Traffic Signal Control on Everett
Street with Stop Sign Control on19th Avenue |
| This option proposes the use of signal control on the major approaches
(Everett Street) including the pedestrian crossing and stop sign control on the minor
approaches (19th Avenue). All approaches to the intersection remain open with all
movements allowed. |
| Option 4: Traffic Signal Control-Complete
Closure of 19th Avenue West Leg |
| Option 4 proposes the closure of the west leg (NE 19th Avenue) of the
intersection to vehicular traffic. This creates a T-intersection with the east leg of NE
19th Avenue and NE Everett Street. |
| Decision Process |
| A consensus was reached between the City of Camas, Washington State DOT,
local police, school district, the city council, and neighborhood citizens which
identified Option 1A (a slight modification of Option 1) as the preferred option. In
addition to those features included with Option 1, Option 1A includes a shortening of the
northern most island to accommodate vehicles turning left from eastbound 19th Avenue to
northbound Everett Street (see the attached plan). This option was chosen for the
following reasons: |
- Delay is minimized for vehicular traffic, bicyclists, and pedestrians.
|
- All approaches to the intersection remain open.
|
- Pedestrians cross only one lane of traffic at a time.
|
- Curb cut design through raised median positions pedestrians and bicyclists to be facing
in the direction of oncoming vehicular traffic.
|
- Construction, maintenance, and operation costs are less than for a signalized
intersection.
|
- Passive control means beacons would be active only when pedestrians are present. This is
believed to keep motorists from becoming conditioned to the warning devices and eventually
ignoring them.
|
- Since there are no timers required to activate the beacons, supplementary warning of
pedestrians and bicyclists would be available 24 hours a day.
|
- Lane restrictions due to islands are designed to slow traffic through crossing area.
|
- Since pedestrians cross only one lane of traffic at a time, the number of available gaps
will increase.
|
| Aesthetics of the area would not be greatly changed. Mast arm poles would
be kept to a minimum and there would be no large controller cabinets. |
- Left turns eastbound on 19th Avenue would not be restricted.
|
- Northbound left turns on Everett Street would be prohibited keeping congestion due to
these turning vehicles to a minimum.
|
| Evaluation Tests |
| The use of passive detection methods at pedestrian crossings to activate
supplemental warning or traffic signal devices is a relatively new concept in the United
States. With the addition of traffic calming elements and the use of passive detection to
activate supplemental warning devices at this crossing, it is desirable to evaluate the
crossing to determine if any of the treatments changed motorist or pedestrian behaviors
within the crossing area. With approval of the Washington State Department of
Transportation and the City of Camas Public Works, three different surveys will be
conducted before and after the addition of the crossing treatment to evaluate it=s effectiveness. The following is a list of these
studies and what is expected to be concluded from them. |
- Speed Surveys: Conducted to evaluate if lane width restrictions and the addition of
supplemental warning beacons and crossing signs change motorists behavior within the
crossing area.
|
- Pedestrian Crossing: These counts will be conducted at adjacent intersections and Counts
Survey mid-block locations as well as the crossing itself. Before counts will show where
pedestrians are currently crossing Everett Street. After counts will make it possible to
determine if modifications to the existing crossing has encouraged pedestrians to use the
crossing, cross at other locations, or if pedestrian behaviors remain unchanged.
|
- Video Tape Survey: Video taping will be conducted on both approaches of Everett Street.
Cameras will be placed in advance of the crossing (approximately 100 to 200 feet in
inconspicuous locations) at a position that will allow both the taillights of braking
vehicles and the complete crossing area to be monitored. By observing the brake lights of
passing vehicles, the reactions of motorists to pedestrians at the crossing can be
determined. Since the complete crossing is monitored, the behavior of the pedestrian at
the crossing can also be determined.
|
| Conclusion |
| The use of passive detection methods to activate supplemental warning
devices at unsignalized crossings or even to replace pushbuttons at signalized pedestrian
crossings is another alternative to help increase crossing safety for both motorists and
pedestrians. Test sites such as the one being developed for the City of Camas help to
continue the development of new ideas and equipment that can provide safer and more
efficient transportation facilities for all modes of travel. |
| References |
| 1 Beckwith D., and K. Hunter-Zaworski. Passive Pedestrian Detection at
unsignalized Crossings. Transportation Research Board Preprint, National Research
Council, Washington, D. C., 1998. |