The Traffic Investigations Section undertook a traffic calming project in the summer of 1999 to address traffic problems identified by the Audubon Society of Portland on NW Cornell Road between NW 53rd and NW30th Avenues, in front of the Audubon Society Visitors Center.
NW Cornell Road is a Neighborhood Collector that serves single family residences in unincorporated Multnomah and Washington Counties. The portion of Cornell Road near the Audubon Society is a forested, winding, rural road with almost no development adjacent to the street. NW Cornell has neither sidewalks nor curbs but there are several park trails crossing Cornell Road at various locations. Additionally, there are horizontal and vertical curves that limit sight distances.
The Audubon Society is concerned with pedestrian safety and driver speeds in front of their business. Approximately 50,000 people visit the Audubon Society annually, including many school age children. Additionally, there are many park trails that cross Cornell Road in this vicinity. The high automobile speeds make it difficult for pedestrians to safely judge crossing opportunities. Additionally, the horizontal curves in the roadway are hard for vehicles to negotiate at high speeds and have caused several accidents near the Audubon Society.
Previous requests for pedestrian improvements resulted in the installation of pedestrian advance signs and curve warning signs. Neither appears to have improved the problem. Traffic Management considered the installation of a pedestrian signal but this was rejected due to the long crossing area, inadequate sight distance for the signal heads and concerns about signal violation (signal does not meet warrants). The Audubon Society has proposed speed bumps in the past but Cornell Road was identified as an emergency response route until 1998, when the Fire Bureau removed that designation.
The main goal for the Audubon Society and the City of Portland was to reduce vehicle speeds in the vicinity of the Audubon House and pedestrian crossing area. Reduced vehicle speeds will reduce the required stopping sight distance near the crosswalk, which is limited due to the horizontal curve. Reduced speeds will also increase the number of gaps for pedestrians crossing Cornell Road.
Two 22-foot speed bumps are proposed near Audubon House, one on either side of the marked crosswalk. The bumps should reduce vehicle speeds to 30 mph near the crosswalk, making it easier for pedestrians to see approaching vehicles and judge crossing opportunities. They will also slow vehicles through the curve where several accidents have been reported, many due to excessive speeds.
The project was coordinated with the Audubon Society. A public open house was not held since the Audubon Society and Forest Park own the property adjacent to the project.
The Bureau of Maintenance constructed two 22-foot speed bumps, spaced 385 feet apart, near the Audubon House on NW Cornell Road on June 18, 1999.
As the graph shows, vehicle speeds, previously concentrated between 38 and 41 mph, have been shifted into the range of 30 to 37 mph. The average 85th percentile speed before the project was 39 mph. Since bump construction the average 85th percentile speed is 33 mph and ranges from a low of 30 mph (at the crosswalk) to a high of 37 mph. Before installation of the speed bumps 29-60% of drivers exceeded the posted speed limit of 35 mph and 1-4% exceeded the limit by 10 mph or more. Since bump construction 2-22% of drivers exceed the posted speed limit and 0-1% exceed the limit by 10 mph or more.
Traffic volumes measured before bump construction averaged 8293 vehicles per day (vpd) and varied from 8015 to 8645 vpd. After bump construction volumes averaged 7943 vpd and varied from 7694 to 8276 vpd.
Traffic volumes were not measured on adjacent streets since Cornell Road is rural and there are no parallel local streets that would allow for diversion. The best alternate route to Cornell Road is NW Skyline to NW Burnside, neither of which are local service streets.
The NW Cornell Road Traffic Calming Project has succeeded in meeting the primary goal of reducing vehicle speeds near Audubon House. 85th-percentile speeds have been reduced from 39 mph to 31 mph at the crosswalk. The Audubon Society perceives that traffic is slowing through the area and is pleased with the project.
Traffic Calming on NW Cornell Road at Audubon House has enhanced pedestrian safety as well as street and driver safety.