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24 suit by lowering the speed limit on the adjacent roadway most of the intersections have static signs. In the 1.8-mile Cen- to 30 mph. Since the beginning of operation, they have tral Platte Valley spur, there are a few gate-protected crossings. only experienced 11 left-turn collisions, which have been widely distributed across the many crossings along the corridor (there has not been more than one left-turn High Collision Locations collision at any one intersection). RTD's collision experience has been concentrated generally · Signal pre-emption phasing. Initially, after an LRV pre- in a few locations. The high collision locations are discussed empted a signal, the signal would go back to the "start," in more detail here. which was a green for the cross-street traffic. In the case that the protected left-turn phase was pre-empted, this phase would be skipped and motorists turning left would Colfax Avenue and 7th Street have to wait through another cycle. When the protected left-turn phase is skipped, some motorists may think that The intersection of Colfax and 7th Street carries high volumes the signal has failed and then make the decision to violate of automobile traffic. Colfax is a six-lane major arterial, and the signal. In response, TriMet tested software that would 7th Street leads into the Auraria Higher Education Center. It return the signal to the phase that was pre-empted. is also a complicated intersection from a geometric perspec- Although this appeared to work, its use has not been well tive, as 7th Street intersects Colfax on a slight curve from the institutionalized across TriMet's light rail system. north. There is a left-turn pocket lane for motorists turning · Increasing permissible traffic movements. Prior to the left from Colfax onto 7th Street. The left turn operates with LRT line, motorists were allowed to make permissive protected-permitted phasing owing to the traffic volumes at left turns at Morrison Street in downtown Portland. Dur- the intersection. ing the start-up phase of the LRT line, left turns were prohibited at Morrison Street; however, they were still At this intersection, RTD experiences collisions between allowed after an all-red phase on Yamhill Street, which motorists making left turns from Colfax onto 7th Street and runs parallel to Morrison Street. During the first year of LRVs approaching from behind, between motorists making operation, there were no collisions on Yamhill Street, right turns from Colfax onto 7th Street and LRVs approaching despite the permissive left turns, although there were sev- from behind, and between motorists making right turns from eral collisions on Morrison Street. Morrison was there- 7th Street onto Colfax and LRVs approaching from either fore changed to permit left turns in the same manner as direction. RTD believes that the primary reasons why colli- Yamhill and both collisions and near-miss incidents sions occur at this intersection are that it is a complicated, busy decreased considerably (4). intersection and that motorists are either not paying enough · Public education. Five to 6 years ago, TriMet worked to attention or they do not understand why they are not allowed add nearly a page of language to the state driver's manual to turn. that specifically related to driving around LRT vehicles. To control permissive right turns at this location, RTD used As a result of their efforts, TriMet has significantly reduced static "No Right Turn When Flashing" signs associated with a their collision occurrence. On average, in the 4-year period flashing yellow light (Figure 28); however, this did not work between 1994 and 1997, TriMet experienced one collision well. Drivers did not know why they were not allowed to turn every 33,368 train-miles. (Collisions include every incident of contact, including minor fender benders, clipped mirrors, and many other incidents in which no injuries were reported and material damage was minimal.) On average, in the 4-year period between 2004 and 2007, they experienced one collision every 93,492 miles. DENVER REGIONAL TRANSPORTATION DISTRICT RTD began their LRT operation in 1994 with the 5.3-mile Central Corridor. Since then, they have expanded by adding 8 miles in 2000, 1.8 miles in 2001, and 19 miles in 2006, for a total of about 34 miles of track. RTD's street-running opera- tions run from about 10th and Osage south of downtown Denver into and around downtown. Within the street-running section, there are approximately 35 intersections, includ- ing driveways. Along California and Stout, the LRT runs con- tra flow to two lanes of one-way automobile traffic. The track FIGURE 28 No Right Turn When Flashing sign from Colfax is separated by a 4-in. to 6-in. mountable curb. Downtown, Avenue to 7th Street in Denver.
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25 when the globe was flashing, so they turned anyway and some The LRT runs parallel to Stout. At this intersection (effectively were struck by LRVs. RTD has replaced these signs with two intersections), collisions occur between motorists travel- LRV-activated turn-prohibition signs (Figure 29), which acti- ing eastbound and westbound on Speer by running the red vate when turns are prohibited, and these signs work better at lights and colliding with the LRVs at a right-angle, and colli- controlling right turns than the flashing yellow. However, sions between motorists making left turns from eastbound there are still drivers who violate the signs. RTD plans to add Speer onto northbound Stout. the LRV-activated train-approaching warning signs to provide additional information to drivers about why they are not Left turns from Stout onto westbound Speer (i.e., one-way allowed to turn. northbound to one-way westbound) and left turns from Speer onto Stout (i.e., one-way eastbound to one-way northbound) In response to right-turn motorists exhibiting risky behav- are not permitted on red, as motorists must cross the LRT iors, including violating the active "No Right Turn" sign on the tracks when turning left. Left turns are allowed only during the 7th Street approach at this intersection, RTD and the Univer- protected left-turn signal phase; left turns are prohibited at all sity of Colorado, Denver, conducted a study (7). In an attempt other times with the use of red arrow signal displays and a sign to reduce risky behaviors by motorists, they implemented three reading "Left on Green Arrow Only." In RTD's experience, treatments, which included the red arrow signal displays work better than red balls and "No Turn on Red" signs. Motorists have more respect for the · Extending the concrete apron 8 ft further in the right- red arrow signal displays than the static signs, as they will vio- turn lane, which created a visual contrast of the road- late the signs more often than the signals. way surface to help approaching motorists identify the LRTroadway crossing; · Moving the stop bar on the 7th Street approach 5 ft further Welton Corridor upstream (from 15 ft upstream to 20 ft upstream); and. · Re-applying all pavement markings. The Welton corridor is along the D Line north of downtown. Welton is a one-way street running northbound. There is a The researchers defined several categories of risky behav- short section of single track that runs bi-directionally. There iors or "traffic violations," including stopping 2 to 4 ft past the are a couple of intersections with traffic signals. At these stop bar, stopping 6 ft past the stop bar, maneuvering before locations, RTD experiences collisions between motorists the track, stopping within 4 to 6 ft of the near rail, not stopping approaching Welton from the east who must cross the track at the flashing no turn sign, and reversing on the tracks. A before entering the intersection at Welton. Motorists making before-and-after analysis revealed a significant decrease in right turns on red will encroach on the tracks to look to the left total risky behaviors by motorists after the treatments were for a gap in traffic and then get struck by an LRV approach- installed. ing from the right. At these intersections, there is a sign that reads, "Train Approaching When Flashing," with an asso- ciated flashing yellow light that activates when the train is Speer Boulevard and Stout Street approaching. This sign has been in place since the line opened. No other countermeasures have been implemented to mitigate The intersection of Speer and Stout is unique. Speer is an these collisions. eight-lane major arterial. The two directions are separated by a creek; thus, Speer operates like a one-way pair. Stout is a one-way street running northbound into downtown Denver. Considerations During Planning Stages Based on the experience at RTD, several considerations were noted for agencies in the planning stages of LRT: · Design and engineer out the big hazards. For example, sharing the left-turn lane is confusing for motorists; they do not know when they can be in the lane and when they cannot. Even if the signage appears to be clear, it may not be. · Prohibit movements when possible. When movements are permitted sometimes and prohibited other times, motorists get mixed messages that can lead to problems. Prohibiting movements, however, can be difficult in street-running environments where the city needs to keep traffic moving. FIGURE 29 LRV-activated turn prohibition signs--7th Street to · Educate the public beforehand. Educating the public is Colfax Avenue in Denver. critical, especially if there is part of the design that could