National Academies Press: OpenBook
« Previous: Chapter Four - Case Studies
Page 33
Suggested Citation:"Chapter Five - Conclusions." National Academies of Sciences, Engineering, and Medicine. 2008. Light Rail Vehicle Collisions with Vehicles at Signalized Intersections. Washington, DC: The National Academies Press. doi: 10.17226/14215.
×
Page 33
Page 34
Suggested Citation:"Chapter Five - Conclusions." National Academies of Sciences, Engineering, and Medicine. 2008. Light Rail Vehicle Collisions with Vehicles at Signalized Intersections. Washington, DC: The National Academies Press. doi: 10.17226/14215.
×
Page 34
Page 35
Suggested Citation:"Chapter Five - Conclusions." National Academies of Sciences, Engineering, and Medicine. 2008. Light Rail Vehicle Collisions with Vehicles at Signalized Intersections. Washington, DC: The National Academies Press. doi: 10.17226/14215.
×
Page 35
Page 36
Suggested Citation:"Chapter Five - Conclusions." National Academies of Sciences, Engineering, and Medicine. 2008. Light Rail Vehicle Collisions with Vehicles at Signalized Intersections. Washington, DC: The National Academies Press. doi: 10.17226/14215.
×
Page 36
Page 37
Suggested Citation:"Chapter Five - Conclusions." National Academies of Sciences, Engineering, and Medicine. 2008. Light Rail Vehicle Collisions with Vehicles at Signalized Intersections. Washington, DC: The National Academies Press. doi: 10.17226/14215.
×
Page 37

Below is the uncorrected machine-read text of this chapter, intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text of each book. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

33 SUMMARY OF RESULTS The placement of light rail transit (LRT) in the median, adja- cent to an urban street, or within an urban street can lead to complex grade crossings incorporated into signalized highway intersections. These intersections have unique operating char- acteristics and have been proven to create problems that can lead to collisions between light rail vehicles (LRVs) and motor vehicles. Although the types of collisions that occur at these intersections tend to vary between agencies, the collisions are almost always a result of the motorists making an illegal turn in front of an approaching LRV and/or running a red signal indication. Based on a review of the most recent literature and structured telephone interviews with selected transit agencies, the most common six scenarios of LRV–motor vehicle colli- sions have been characterized as the following: • Motorists in left-turn pocket lanes violate the red left-turn signal indication and collide with LRVs approaching from behind (median-running, side-running, mixed-use). • Motorists make illegal left turns against static turn no left- turn signs (at locations where turns are prohibited) and collide with LRVs approaching from behind (median- running, mixed-use). • Motorists violate active turn-prohibition signs and train- approaching signs in conflict with LRV operation (at locations where turns are permitted or prohibited). • Motorists make left turns from adjacent through-only lanes instead of from the lanes shared with the LRVs (mixed-use). • Drivers encroach on or stop on the tracks and are struck by an LRV (coming from either direction) at a right angle (side-running). • Drivers run a red signal indication and collide with an LRV (coming from either direction) at a right angle (median-running, mixed-use, pedestrian mall). Based on the results of a literature review and the structured telephone interviews, the possible causes of each of these six scenarios are summarized in Tables 4 through 9, and they are linked to the potential engineering countermeasures discussed in chapter three for mitigating inappropriate and risky motorist behaviors and collisions. In addition to the engineering countermeasures specific to the different collision scenarios, public education and enforce- ment play a vital role in LRT safety in localities where the pub- lic may not be familiar with LRT operations or where blatant violations (such as speeding to beat the train to the crossing) are occurring. Recommendations for education and enforce- ment include • Focusing public education and outreach programs on how and when to make left turns along the LRT line and the importance of obeying traffic regulations. • Including education materials informing that left turns can be accomplished by making three right turns. • Emphasizing in the public education program the impor- tance of driving defensively and that traffic regulations are intended to keep the traveling public safe. • Prominently displaying safety education materials in businesses and commercial buildings in localities along the LRT alignment having a high rate of noncompliance with traffic regulations. • Distributing, by location, pamphlets to passing motorists and pedestrians. • Assigning police to enforce traffic regulations, with emphasis on turn violations and running red lights. • Keeping police officers visible to remind drivers to obey traffic regulations. • Publicizing the enforcement program to encourage drivers to take traffic regulations more seriously. • Considering the use of photo enforcement, which has been an effective means of improving driver compliance with control devices in Los Angeles. CONCLUSIONS There are a number of different types of collisions that occur between LRVs and motor vehicles at signalized intersections. While left-turn collisions appear to make up the greatest percentage of these collisions, right-angle col- lisions owing to motorists running red lights on the cross street are also a problem for many agencies. The large major- ity of LRV–motor vehicle collisions appear to be caused by motorists making illegal maneuvers in front of LRVs. Transit agencies have approached the LRV–motor vehicle collision problem using a variety of different countermeasures, including physical barriers, traffic signs, traffic signal displays, signal phasing, pavement treatments and markings, education, and enforcement. The most effective means of mitigating collisions between LRVs and motor vehicles at signalized intersections is to physically separate LRV and motor vehicle movements by CHAPTER FIVE CONCLUSIONS

providing exclusive rights-of-way and grade-separated cross- ings. In semi-exclusive rights-of-way, physical separation of LRV and vehicle movements can be accomplished through the use of full-closure or four-quadrant gate systems or through the combined use of raised medians and two-quadrant gates. This practice has been effective for many transit agen- cies; however, there are drawbacks to the use of gates. Often times the footprint of the gates is too big, cost can be an issue, the gates have to fit into the cityscape, and there are noise and aesthetic considerations. In semi-exclusive and non-exclusive environments where LRVs operate at speeds of 35 mph or less and physical sepa- ration of LRV and motor vehicle movements is not practical or affordable, LRV–motor vehicle collisions must be mitigated through traffic control. Because a large number of collisions are caused by motorist error or misperception, giving motorists enough of the right information, without giving them too much information, seems to be a key factor in mitigating risky behavior and potentially collisions. Motorists need positive guidance, which can be provided through signal displays (e.g., green or red arrow aspects), signs (e.g., lane-use signs), and pavement markings (e.g., lane-use arrows). Motorists also need sufficient information to help them make the right deci- 34 sions. For example, it has been proven that simply telling motorists that turns are prohibited is not always enough to keep them from doing so. Motorists’ experiences at conventional intersections may have shown them that violating a “No Turn on Red” or a “No Turns” sign has little consequence. Although this may or may not be the case at conventional intersections, it almost certainly is not the case with the added complexity at intersections that incorporate LRT. Therefore, providing the extra information about why turns are prohibited (e.g., active train-approaching warning signs) should help give motorists the additional information to make the right decisions. This approach appears to have been effective for transit agencies including TriMet, Hous- ton METRO, and DART. Public education and enforcement are also critical elements to mitigating collisions between LRVs and motor vehicles. Police and photo enforcement have been effective approaches to mitigating risky behaviors and collisions in Los Angeles. Despite the efforts put forth by transit agencies and city and county traffic engineering departments, collisions between LRVs and motor vehicles at signalized intersections continue to occur, and agencies continue to seek out innovative counter- Possible Cause Possible Engineering Counterm easures Signs do not convey to mo torists why they are not allowed to turn. Install LRV-activated train-approaching warning signs to provide additional inform ation to drivers about why they are not allowed to turn and the consequences of ma king an illegal left turn against the traffic signal. Motorists initiate their left turns against the signal as soon as the cross-street traffic receives the red (particularly co mm on at locations with leading left-turn phases). Change the left-turn signal phase from a leading left to a lagging left. Motorists in the left-turn lane mistake the through-traffic signals for those controlling the left-turn movement. Use green arrows aspects for through traffic, which provide positive guidance by clearly indicating the perm itted m ovem ent. Use programmable visibility signal heads to reduce the visibility of the through-traffic signals from the left-turn lanes. Motorists in the left-turn lane cue off of the m ovem ent of the through vehicles. Im plem ent an all-red phase as trains pass through intersections so that no vehicular traffic is moving as the trains pass through the intersection. Use red left-turn arrow instead of red ball to provide positive guidance. Motorists ma ke left turns across the LRT right-of-way i mme diately after term ination of their green left-turn arrow. Change the left-turn signal phase from a leading left to a lagging left. Motorists confuse LRT signals with traffic signals. Use LRT bar signals. Where traffic signals are pre-em pted during the left-turn phase, motorists may incorrectly assum e that the signal failed and violate the signal. Use signal system that returns to the phase that was pre- em pted. TABLE 4 SCENARIO: MOTORISTS IN LEFT-TURN POCKET LANES VIOLATE THE RED LEFT-TURN SIGNAL INDICATION AND COLLIDE WITH LRVS APPROACHING FROM BEHIND

35 TABLE 5 SCENARIO: MOTORISTS MAKE ILLEGAL LEFT TURNS AGAINST STATIC TURN NO LEFT-TURN SIGNS AND COLLIDE WITH LRVS APPROACHING FROM BEHIND Possible Cause Possible Engineering Countermeasures There may be too few locations to make left turns across the tracks leading to increased pressure to turn left where such movements can be made, even if prohibited. Post advance signs showing that upcoming left turns can be accomplished by making three right turns starting beyond the cross street. Provide an all-red phase to permit LRV movement at the end of the cross- street green phase. Motorists who are used to violating regulatory signs with little consequence at conventional signalized intersections need to better understand the risks of violating turn prohibitions at intersections with LRT. Give LRVs a brief ìq ueue jump” or “head start” of 2 to 4 s before motor traffic after a red signal to establish LRV presence at the intersection and to prevent illegal left turns. There are too many signs at intersections. Multiple signs increase driver information processing time and increase the potential for missing important information. Consolidate traffic sign messages where possible, and eliminate unnecessary redundancies. Combine the “No Left Turn” and “No U-Turn” signs into the R3-18 combination symbol sign. Place left- and U-turn prohibition signs in the median, on the far-left side, or on the left side of the signal mast arm. Do not place left- or U-turn prohibition signs on the right side of the intersection. Place right-turn prohibition signs only on the right side of the intersection. When both right- and left-turns area is prohibited at an intersection, use the “No Turn” sign (R3-3) on the signal mast arm. Traffic control devices place an emphasis on prohibited rather than permitted movements. Drivers may be confused about where they can make turn movements and where a through movement is the only permitted movement. Displaying permitted movements provides positive guidance, could ease decision load on drivers, and results in fewer last-second decisions in complex driving conditions. Use overhead lane-use control signs in place of extra turn-prohibition signs; each prohibited movement should be included at least once on turn- prohibition signs. Use (turn) ONLY signs where there is only one permitted movement at an intersection. Use green arrow aspects on traffic signal heads instead of green ball and redundant turn-prohibition signs. Provide lane-use markings in individual lanes on the approach to signalized intersections. By providing markings on the pavement, drivers are more likely to see them. Markings should be placed so that they are not concealed by the first one or two vehicles in the queue. Supplement the lane-use arrows with the word ONLY when only one movement is permitted from the lane. measures in an effort to further reduce the frequency and severity of these collisions. The findings suggest the need for the following areas of research: • Success and/or effectiveness of the countermeasures being used by agencies. Transit agencies have taken a number of approaches and implemented a variety of countermeasures to mitigate collisions between LRVs and motor vehicles at signalized intersections. Although some of these countermeasures have been more effective than others from the perspective of the agencies, there have been few empirical studies conducted to examine the effectiveness of the countermeasures in terms of driver compliance, collision frequency, or collision severity. More research is needed to better understand the effectiveness of many of the countermeasures in terms of collision mitigation and prevention. • Use of Chapter 10 of the Manual on Uniform Traffic Control Devices for Streets and Highways (MUTCD). This research has revealed a variety of countermeasures being used by agencies to mitigate collisions between LRVs and motor vehicles at signalized intersections; however, some of the countermeasures being used are not necessarily consistent with those in Chapter 10 of the MUTCD. In particular, agencies are using a variety of train warning signs and no turn signs. More research is needed to better understand why agencies do not always use the warning and control devices recommended in the MUTCD and what impact these inconsistencies have on safety.

36 Possible Cause Possible Engineering Countermeasures Active signs may be activated too far in advance of arrival of the LRV. Use train-activation system to activate train-approaching warning signs. Signs may be activated too late to provide sufficient advance warning to motorists. Use train-activation system to activate train-approaching warning signs. Motorists do not understand why the signs are on and/or why turns are prohibited. Permitting movements at some times and prohibiting them at others causes driver confusion. Install train-approaching warning signs. Install active TRAIN COMING educational plaque below the turn-prohibition signs. Make movement protected-only. TABLE 6 SCENARIO: MOTORISTS VIOLATE ACTIVE TURN-PROHIBITION SIGNS AND TRAIN-APPROACHING SIGNS IN CONFLICT WITH LRV OPERATION Possible Cause Possible Engineering Countermeasures Drivers are confused about which lane to turn from. Use pavement marking arrows indicating allowable movements and ONLY (where appropriate). Use overhead lane-use signs indicating allowable movements and ONLY (where appropriate). Use a programmable left-turn signal head. Queue jump the LRV 3 to 4 s through the intersection where left turns are permitted to enable the LRV to control the intersection and block improper left turns. Install overhead advance intersection lane-use control signs (R3-8). TABLE 7 SCENARIO: MOTORISTS MAKE LEFT TURNS FROM ADJACENT THROUGH-ONLY LANES INSTEAD OF FROM THE LANES SHARED WITH THE LRVS Issue/Problem Possible Cause Possible Engineering Countermeasures Having too many transverse markings on the roadway in the vicinity of the intersection (e.g., crosswalk, stop line, railroad markings) can cause confusion about where to stop. Reduce the number of transverse lines by using an alternative pattern for crosswalk markings. Use contrasting pavements on the near and far sides of the stop bar to increase visibility of the stop bar. Where applicable, relocate pavement markings further upstream of the intersection. Motorists may not perceive the LRT tracks crossing the approach prior to the intersection. Improve the conspicuity of the tracks by using a contrasting pavement treatment. Drivers encroach on or stop on the tracks and get hit by an LRV at a right angle. Motorists attempt right/left turns on red and stop on the tracks to wait for a gap in traffic as the LRV approaches. If applicable, relocate the stop bar further upstream of the intersection. Install crosshatch pavement markings to designate area where motorists should not be stopped. TABLE 8 SCENARIO: DRIVERS ENCROACH UPON OR STOP ON THE TRACKS AND ARE STRUCK BY AN LRV AT A RIGHT ANGLE

37 TABLE 9 SCENARIO: DRIVERS RUN A RED SIGNAL INDICATION AND COLLIDE WITH AN LRV AT A RIGHT ANGLE Issue/Problem Possible Cause Possible Engineering Countermeasures Drivers run a red signal indication and collide with an LRV at a right angle. Motorists are unaware an LRV is coming or speed through the intersection in an attempt to beat an approaching LRV. Install in-roadway lights. Install LRV-activated train-approaching warning signs on cross-street approach (showing side-view/profile of LRV).

Next: References »
Light Rail Vehicle Collisions with Vehicles at Signalized Intersections Get This Book
×
MyNAP members save 10% online.
Login or Register to save!
Download Free PDF

TRB's Transit Cooperative Research Program (TCRP) Synthesis 79: Light Rail Vehicle Collisions with Vehicles at Signalized Intersections explores mitigation methods tested and used by transit agencies to reduce collisions between light rail vehicles (LRVs) and motor vehicles where light rail transit (LRT) runs through or adjacent to highway intersections controlled by conventional traffic signals.

  1. ×

    Welcome to OpenBook!

    You're looking at OpenBook, NAP.edu's online reading room since 1999. Based on feedback from you, our users, we've made some improvements that make it easier than ever to read thousands of publications on our website.

    Do you want to take a quick tour of the OpenBook's features?

    No Thanks Take a Tour »
  2. ×

    Show this book's table of contents, where you can jump to any chapter by name.

    « Back Next »
  3. ×

    ...or use these buttons to go back to the previous chapter or skip to the next one.

    « Back Next »
  4. ×

    Jump up to the previous page or down to the next one. Also, you can type in a page number and press Enter to go directly to that page in the book.

    « Back Next »
  5. ×

    To search the entire text of this book, type in your search term here and press Enter.

    « Back Next »
  6. ×

    Share a link to this book page on your preferred social network or via email.

    « Back Next »
  7. ×

    View our suggested citation for this chapter.

    « Back Next »
  8. ×

    Ready to take your reading offline? Click here to buy this book in print or download it as a free PDF, if available.

    « Back Next »
Stay Connected!