Boundary to Nebraska
Final Project Evaluation
SW Corbett, Boundary to Nebraska (Lower Corbett), is the designated second phase of the SW Corbett/Virginia corridor project . SW Corbett extends north of Boundary (Phase 3) and south of Nebraska. The portion of SW Corbett south of Nebraska is designated "Upper Corbett" due to its situation uphill from Nebraska. Phase One of this corridor treatment involved a project on SW Virginia, a parallel street to Corbett, which functions as a connecting route to Taylor's Ferry Road.
SW Corbett is designated as a Local Service street but functions as a collector. Corbett, north of Boundary, has an off-ramp from Interstate 5, and connects directly to downtown Portland, making it a convenient commuter route. SW Corbett serves a mixed single-family, apartment and commercial neighborhood. There is an concentrated commercial area at the north end, Boundary Street. The street is straight with a slight hill at the south end, which crests at SW Iowa. There are curbs and sidewalks on both sides of the street. The street is a designated Primary Fire Response Route as well as Transit Route.
The neighborhood traffic committee, formed as part of the traffic calming project, decided that diversion on this street would be difficult to promote and focused their efforts on increasing the street's ambiance and use by pedestrians and cyclists. The committee was formed following a public meeting to discuss the project with area residents. As originally conceived, it was a single project that extended from Taylor's Ferry to Portland Central Business District on Virginia and Corbett. However, additional evaluation and community input resulted in separating the project into three phases. Even though Phase 1 focused on SW Virginia, the initial signature gathering and area wide meeting involved residents on SW Corbett south of Boundary; therefore, the two elements were not repeated for Phase 2. A committee was therefore formed following the public meeting organized by the neighborhood association. Committee and staff developed the following project goals:
1. Improve neighborhood livability and appearance of SW Corbett Avenue.
2. Discourage on-street parking and improve access to businesses.
3. Encourage residents to choose walking as an alternative form of transportation for short trips.
4. Encourage bicycling and promote the safety of bicyclists.
5. Minimize project impact on emergency service vehicles and Tri-Met bus operation.
The devices agreed upon for construction include curb extensions at Pendleton, Flower and Boundary, pedestrian refuges at Carolina and Iowa, a textured cross walk at Boundary, a median barrier north of Sweeney, centerline re-striping and raised pavement markers at Nebraska. Additionally, SW Corbett's speed zone was reduced from 30 mph to 25 mph after construction was completed in November, 1996.
As Graph 1 shows, vehicle speeds have been shifted from a peak of 29-34 mph to 26 to 31 mph.
The average 85th percentile vehicle speed before the project was 35.5 mph and ranged from a low of 34 mph to a high of 37 mph. Since construction the average 85th percentile speed is 31.2 mph and ranges from a low of 24.5 mph to a high of 35.9 mph. Graph 2 and Graph 3 show how the percent of drivers exceeding the speed limit has been reduced.
Traffic volumes measured on SW Corbett before the project averaged 4600 vehicles per day (vpd) and varied from 2700 to 5400 vpd. Higher volumes are consistently measured at the north end of the project due to the high level of commercial use at Boundary. Post-construction volumes averaged 4500 vpd and varied from 3100 to 6900 vpd. Graph 4 describes the distribution of traffic volume over a 24-hour period. As can be seen the traffic pattern has not significantly changed.
SW Nebraska, east of Corbett, and SW Virginia, south of Nebraska, continue a traditional pathway through the neighborhood, to reach Taylor's Ferry Road, avoiding SW Macadam. The traffic volume on SW Nebraska, between Corbett and Virginia, measured before construction averaged 2300 vpd and after construction measured 2200 vpd. The traffic volume measured on SW Virginia, before construction and south of Nebraska, was 2900 vehicles per day (vpd). Traffic volume measured after construction, south of Idaho, was 2600 vpd. The decrease in automobile traffic on both SW Nebraska and SW Virginia is not significant and can be attributed to normal daily traffic fluctuations (+/- 10%).
A committee member expressed concern regarding the remaining vehicle traffic on SW Virginia after completion of Phase One. The committee decided that additional monitoring of the bus-only lane at Taylor's Ferry Road was needed to ensure continued compliance. A review of the bus-only lane was conducted on April 18, 1997. Five violations were observed in a 30 minute period during the peak AM commute. A report of the violations was forwarded to the Traffic Division of the Police Department.
Some members of the committee, as well as residents, expressed concern that automobile traffic might shift to SW Idaho after the project was complete. SW Idaho is south of, and parallels, SW Nebraska between Corbett and Virginia.
The traffic volume measured before construction was 450 vehicles per day (vpd). Traffic volume measured after construction averaged 500 vpd. The 50 vpd increase in automobile traffic is not significant and can be attributed to normal daily traffic fluctuations (+/- 10%).
Three 14-foot speed bumps, at 540 to 620 foot spacing, were constructed along the 0.31 mile stretch of SW Corbett, Custer to Texas, in June of 1996 by the Bureau of Maintenance.
As Graph 5 shows, vehicle speeds, previously concentrated between 26 and 31 mph, have been shifted into the range of 20 to 25 mph. The 85th percentile vehicle speed before the project was 33 mph. After bump construction the average 85th percentile speed is 24.9 mph and ranges from a low of 21 mph (near the bumps) to a high of 29 mph.
Traffic volumes measured since speed bump construction show no significant change from the volumes measured before speed bump construction of 1880 vpd.
Vehicle speeds along SW Corbett, Boundary to Nebraska, have been reduced, most significantly where speed bumps were constructed, without traffic volumes being significantly affected. Several intersections have been enhanced in terms of pedestrian safety. Each of these changes contribute toward achieving the neighborhood goals of increasing the street's ambiance, appearance and use by pedestrians and cyclists.