Click for next page ( 7

The National Academies of Sciences, Engineering, and Medicine
500 Fifth St. N.W. | Washington, D.C. 20001

Copyright © National Academy of Sciences. All rights reserved.
Terms of Use and Privacy Statement

Below are the first 10 and last 10 pages of uncorrected machine-read text (when available) of this chapter, followed by the top 30 algorithmically extracted key phrases from the chapter as a whole.
Intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text on the opening pages of each chapter. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

Do not use for reproduction, copying, pasting, or reading; exclusively for search engines.

OCR for page 6
6 CHAPTER TWO COLLISIONS BETWEEN LIGHT RAIL VEHICLES AND MOTOR VEHICLES AT SIGNALIZED INTERSECTIONS The placement of LRT in the middle of, adjacent to, or within turns in front of an LRV approaching the intersection from the an urban street can lead to complex crossings incorporated into opposite direction. Cross traffic red-light running is also of signalized highway intersections. Although these intersections concern at these intersections. are typically protected with conventional traffic signals and supplemental signage regarding the LRT, they do not operate like conventional crossings, nor do they operate like conven- Side-Running Within Roadway Right-of-Way tional signalized intersections. Rather, they are intersections Side-running LRT within the roadway right-of-way (Figure 1b) with unique operating characteristics that have proven to create operates on a paved guideway within the roadway boundaries problems that can lead to collisions between LRVs and motor of one-way streets. The LRT guideway may be separated from vehicles, especially when turning maneuvers are involved. the roadway by a curb or other physical features except for where motor vehicles must cross the light rail tracks to turn LIGHT RAIL TRANSIT ALIGNMENT THROUGH onto the cross street. Challenges encountered at these inter- SIGNALIZED INTERSECTIONS sections are dependent on whether the LRT right-of-way is located to the left or right of the one-way traffic running The diagrams in Figure 1 illustrate a few examples of how parallel to the tracks. With LRT alignments to the left of the LRT can be incorporated into urban street signalized inter- roadway, left turns in front of LRVs approaching on the left sections. The diagrams include a median-running alignment, from behind are the most prevalent accident type, as motorists two side-running alignments, and a mixed-use alignment. may be unaware of the presence of the LRV. Similarly, right Although each of the diagrams shows dual tracks, any of these turns in front of LRVs approaching on the right from behind alignments could include single-track operation and other vari- are the most common incidents occurring when LRT align- ations in the number of traffic lanes where there are traffic ments are to the right of the roadway. As with other inter- movements. These diagrams are shown for example purposes sections, cross-street traffic disobeying traffic signals can only. Even though there are common challenges among the also be problematic. Side-running alignments have the added different alignments, each presents its own unique challenges, challenge of vehicles encroaching onto the tracks where the which are discussed in more detail here. tracks cross the cross-street approach. Median-Running Alignments Side-Running Adjacent to Roadway In median-running alignments (Figure 1a), LRVs operate Side-running adjacent to a roadway (Figure 1c) are LRT align- between the parallel, two-way lanes of an urban street. The ments located outside of a roadway right-of-way. As with side- LRT right-of-way typically is unpaved (except at designated running LRT alignments within the roadway right-of-way, the locations where motor vehicles cross the light rail tracks) and guideway may be physically separated from the roadway by a is separated from the roadway by curbs, and in some cases, curb, landscaping, and/or fencing. Unlike side-running within fencing. Left-turn pocket lanes for motor vehicles are typically the roadway right-of-way, two-way traffic flow on the adja- provided in the parallel running roadways. Motor vehicle cent roadway is common. Challenges are similar to those movements are controlled by traffic signals. Left-turn motor of side-running within the roadway right-of-way--motorists turning in front of LRVs approaching an intersection from vehicle movements are protected through the use of left-turn- behind the motorist, vehicles encroaching onto the tracks on only traffic signal phases so as to control motor vehicle move- the cross-street approach, and motorists running red lights on ments that conflict with LRVs. Reports of violations of the the cross-street. left-turn signal by motorists are not uncommon at these inter- sections. Collisions typically occur when motorists disregard, do not perceive, or misinterpret the left-turn signal and are Mixed-Use Alignments unaware that an LRV in the median is approaching the inter- section from behind. Although less common, collisions also Generally in mixed-use alignments (Figure 1d ), motor vehi- occur when a motorist intending to turn left at an intersection cles and LRVs share the same travel lanes. It is not uncom-