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William W. Hunter, Senior Research Scientist, UNC Highway Safety Research Center
In many bike lane retrofit projects, there is not enough space to mark a minimum 1.2 m (4 ft) bike lane to the left of a right-turn lane. This case study focuses on a combined bicycle lane/right-turn lane used in Eugene, OR, when right-of-way at an intersection was limited. There are standard options for installing or retrofitting bike lanes onto shared roadways. The American Association of State Highway and Transportation Officials Guide for the Development of Bicycle Facilities (1999) shows accepted ways of accommodating bike lanes at intersections. Placement of bike lanes in conjunction with right-turn lane lanes must be done carefully, in that conflicts result between straight-through bicycles and right-turning motor vehicles (Hunter, Stewart, Stutts, Huang, and Pein, 1999). In some cases where insufficient room exists, the bike lane is dropped prior to the intersection. The Oregon Bicycle and Pedestrian Plan (Oregon DOT, 1995) recognizes this limitation and states that when this occurs, “a right-turn lane may be marked and signed as a shared-use lane, to encourage through cyclists to occupy the left portion of the turn lane. This is most successful on slow-speed streets.”
The City of Eugene, OR, has such a shared, narrow right-turn lane in place on 13th Avenue at its intersection with Patterson Street. The avenue leads directly into the University of Oregon campus and has considerable bicycle traffic (see figure 1 — left side diagram). Near campus, 13th Avenue has a speed limit of 48.3 km/h (30 mi/h) and carries 6,000 to 8,000 vehicles per day.
The left side of Figure 1 provides details for 13th and Patterson, which will be referred to hereafter as the narrow-width right-turn lane site. At this site, bicyclists usually approach the intersection in a 1.5 m (5 ft) bike lane at the edge of the street. At the intersection proper, the total right-turn lane width is 3.6 m (12 ft), which includes a bike lane (pocket) of 1.5 m (5 ft) and a 2.1 m (7 ft) space to the right of the bike pocket. The right side of Figure 1 provides details for 13th and Willamette, which will be referred to hereafter as the standard-width right-turn lane site. At this location, bicyclists also usually approach the intersection in a 1.5 m (5 ft) bike lane at the edge of the street. At the intersection proper, the total right-turn lane width is 5.2 m (17 ft), which includes a bike lane (pocket) of 1.5 m (5 ft) and a standard 3.7 m (12 ft) lane to the right of the bike pocket. Figure 1 also shows accompanying signs used at both intersections.
Figure 1. Narrow- and standard-lane views.
The narrow right-turn lane described above was evaluated by comparing the behaviors of bicyclists and motor vehicle drivers at 13th and Patterson (an intersection that had the shared, narrow right-turn lane described above in place) with behaviors at 13th and Willamette (an intersection that had a standard-width (3.7 m (12 ft)) right-turn lane and accompanying bike lane (pocket) to the left of the right-turn lane). The intersection of 13th and Willamette is located about 0.8 km (0.5 mi) west of 13th and Patterson. These right-turn treatments had been in place for several years when this evaluation was done, and bicyclists were familiar with the movements.
It is important to note that bicyclists approaching on 13th at Patterson Street proceed straight ahead to the bike pocket at the intersection proper, in that the right-turn lane is “bulbed out.” Bicyclists approaching on 13th at Willamette have to shift to the left to get in the bike pocket adjacent to the right-turn lane at the intersection (i.e., no “bulb out”).
Approximately 600 bicyclists traveling through each intersection were videotaped during a three-week period in May 1998. Videotaping was done for two-hour periods at different times of the day and week to get a cross-section of bicyclists and to avoid recording bicyclists more than once. It is possible that some duplication occurred, but the number would have been quite small. Figure 2 shows the view from a video camera of oncoming bicyclists at both 13th and Patterson (the narrow-width site) and 13th and Willamette (the standard-width site). The videotapes were coded to evaluate operational behaviors and conflicts with motorists, other bicyclists, and pedestrians. Coded bicyclist variables included sex, age group, helmet use, whether a passenger was being carried, intersection approach position, position at the intersection, proximity of the bicyclist to motor vehicle at a red traffic signal indication, turning movements, traffic signal violations, and whether the bicyclist prevented a right-turn-on-red by following motorist. Coded motor vehicle information included type of motor vehicle beside the bicyclist at a red traffic signal indication, and motor vehicle type and position without a bicyclist present. We also coded whether any conflicts occurred. Conflicts between a bicyclist and a motor vehicle, another bicyclist, or a pedestrian were defined as an interaction such that at least one of the parties had to make a sudden change in speed or direction to avoid the other.
Figure 2. Videotaped bicyclists at the narrow-lane sites (above) and standard-lane sites (below).
The videotapes were coded to evaluate operational behaviors and conflicts with motorists, other bicyclists, and pedestrians. Coded bicyclist variables included sex, age group, helmet use, whether a passenger was being carried, intersection approach position, position at the intersection, proximity of the bicyclist to motor vehicle at a red traffic signal indication, turning movements, traffic signal violations, and whether the bicyclist prevented a right-turn-on-red by following motorist. Coded motor vehicle information included type of motor vehicle beside the bicyclist at a red traffic signal indication, and motor vehicle type and position without a bicyclist present. We also coded whether any conflicts occurred. Conflicts between a bicyclist and a motor vehicle, another bicyclist, or a pedestrian were defined as an interaction such that at least one of the parties had to make a sudden change in speed or direction to avoid the other.
The technique worked well at the intersection locations evaluated in this study. More than 17 percent of the surveyed bicyclists using the narrow-lane intersection felt that it was safer than the comparison location with a standard-width right-turn lane, and another 55 percent felt that the narrow-lane site was no different safety-wise than the standard-width location. This is probably a function not only of relatively slow motor vehicle traffic speeds on 13th Street, but also because of the bike lane proceeding straight through the intersection at the narrow-lane site such that motorists crossing to the right-turn lane tended to have to yield. Bicyclists at the comparison intersection had to shift to the left to be positioned in the bike pocket next to the right-turn lane. It was also relatively easy for bicyclists to time their approach to the narrow-lane intersection and ride through on a green indication.
It was expected that bicyclists going straight through the narrow-lane intersection would position themselves either in front of or behind motorists. However, it was quite easy for bicyclists to ride up to the narrow-lane intersection and position themselves beside passenger cars or light trucks. The issue of the most appropriate position for a bicyclist at an intersection is not necessarily well understood or agreed upon. Positioning certainly can vary as a function of motor vehicle speed, traffic volume, turning movements, and a number of other variables. This evaluation pertains to a single location for this narrow-lane treatment, and it would be beneficial to compare bicyclist positioning choice here to what occurs at other intersection types, such as a shared through/right-turn lane with no bicycle lane or pocket.
Bicyclists at the narrow-lane site chose to position themselves in the adjacent traffic lane on a few occasions, usually the result of a heavy vehicle taking extra space. Sometimes bicyclists would shift to the right-turn portion of the lane if a heavy vehicle were in the through lane. Right turns on red by motor vehicles were rarely prevented when bicyclists were present at the front of the queue at the narrow-lane site. No conflicts between bicyclists and motor vehicles, other bicyclists, or pedestrians took place at either intersection.
The combined bicycle lane/right-turn lane design is shown in the Oregon Bicycle and Pedestrian Plan and has been reviewed, but not yet officially adopted, by the Oregon Department of Transportation’s Traffic Control Device Committee. However, adoption is expected in the near future. For the present, favorable conditions for implementation appear to be on local streets with speeds of 48.3 km/h (30 mi/h) and traffic volumes of less than 10,000 vehicles per day. Adding a bulb-out to the combined bike lane/right-turn lane so that motorists move to the right and bicyclists continue in a straight line may also be a safer situation for bicyclists.
It is recommended that the design be implemented at other types of intersection locations (i.e., different motor vehicle approach speeds and approach configurations) and evaluated for effectiveness.
There are many intersections where using a minimum-width bike lane is not possible due to limited right-of-way. The use of a shared, narrow right-turn lane in combination with a bike lane in a limited right-of-way situation is a novel approach. This treatment could be applied in initial intersection design, when retrofitting a bike lane to an existing right-of-way, and when adding an auxiliary right-turn lane.
Costs included the removal of paint (regular, not thermoplastic), new thermoplastic paint, a sign placed in the ground and another sign next to the signal head for about $1,500 in parts and labor. If traffic loops have to be moved, it would cost an additional $1,000 per lane.
Lee Shoemaker
Bicycle & Pedestrian Program Coordinator
City of Eugene Public Works
858 Pearl Street
Eugene, OR 97401
(541) 682-8472 (voice)
(541) 682-5598 (fax)
lee.shoemaker@ci.eugene.or.us
William Hunter
UNC Highway Safety Research Center
730 Martin Luther King Jr Blvd, Suite 300
Chapel Hill, NC 27599-3430
(919) 962-8716
bill_hunter@unc.edu