Click for next page ( 34


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

OCR for page 33
34 TABLE 4 SCENARIO: MOTORISTS IN LEFT-TURN POCKET LANES VIOLATE THE RED LEFT-TURN SIGNAL INDICATION AND COLLIDE WITH LRVS APPROACHING FROM BEHIND Possible Cause Possible Engineering Countermeasures Signs do not convey to motorists why they Install LRV-activated train-approaching warning signs to are not allowed to turn. provide additional information to drivers about why they are not allowed to turn and the consequences of making an illegal left turn against the traffic signal. Motorists initiate their left turns against the Change the left-turn signal phase from a leading left to a signal as soon as the cross-street traffic lagging left. receives the red (particularly common at locations with leading left-turn phases). Motorists in the left-turn lane mistake the Use green arrows aspects for through traffic, which provide through-traffic signals for those controlling positive guidance by clearly indicating the permitted the left-turn movement. movement. 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 Implement an all-red phase as trains pass through movement of the through vehicles. 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 make left turns across the LRT Change the left-turn signal phase from a leading left to a right-of-way immediately after termination lagging left. of their green left-turn arrow. Motorists confuse LRT signals with traffic Use LRT bar signals. signals. Where traffic signals are pre-empted during Use signal system that returns to the phase that was pre- the left-turn phase, motorists may incorrectly empted. assume that the signal failed and violate the signal. providing exclusive rights-of-way and grade-separated cross- sions. For example, it has been proven that simply telling ings. In semi-exclusive rights-of-way, physical separation of motorists that turns are prohibited is not always enough to keep LRV and vehicle movements can be accomplished through them from doing so. Motorists' experiences at conventional the use of full-closure or four-quadrant gate systems or intersections may have shown them that violating a "No through the combined use of raised medians and two-quadrant Turn on Red" or a "No Turns" sign has little consequence. gates. This practice has been effective for many transit agen- Although this may or may not be the case at conventional cies; however, there are drawbacks to the use of gates. Often intersections, it almost certainly is not the case with the times the footprint of the gates is too big, cost can be an issue, added complexity at intersections that incorporate LRT. the gates have to fit into the cityscape, and there are noise Therefore, providing the extra information about why turns and aesthetic considerations. are prohibited (e.g., active train-approaching warning signs) should help give motorists the additional information to In semi-exclusive and non-exclusive environments where make the right decisions. This approach appears to have LRVs operate at speeds of 35 mph or less and physical sepa- been effective for transit agencies including TriMet, Hous- ration of LRV and motor vehicle movements is not practical or ton METRO, and DART. affordable, LRVmotor vehicle collisions must be mitigated through traffic control. Because a large number of collisions Public education and enforcement are also critical elements are caused by motorist error or misperception, giving motorists to mitigating collisions between LRVs and motor vehicles. enough of the right information, without giving them too much Police and photo enforcement have been effective approaches information, seems to be a key factor in mitigating risky to mitigating risky behaviors and collisions in Los Angeles. behavior and potentially collisions. Motorists need positive guidance, which can be provided through signal displays (e.g., Despite the efforts put forth by transit agencies and city and green or red arrow aspects), signs (e.g., lane-use signs), and county traffic engineering departments, collisions between pavement markings (e.g., lane-use arrows). Motorists also LRVs and motor vehicles at signalized intersections continue need sufficient information to help them make the right deci- to occur, and agencies continue to seek out innovative counter-

OCR for page 33
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 Post advance signs showing that upcoming left turns can be accomplished to make left turns across the by making three right turns starting beyond the cross street. tracks leading to increased Provide an all-red phase to permit LRV movement at the end of the cross- pressure to turn left where such street green phase. movements can be made, even if prohibited. Motorists who are used to Give LRVs a brief q ueue jump" or "head start" of 2 to 4 s before motor violating regulatory signs with traffic after a red signal to establish LRV presence at the intersection and to little consequence at prevent illegal left turns. conventional signalized intersections need to better understand the risks of violating turn prohibitions at intersections with LRT. There are too many signs at Consolidate traffic sign messages where possible, and eliminate unnecessary intersections. Multiple signs redundancies. increase driver information Combine the "No Left Turn" and "No U-Turn" signs into the R3-18 processing time and increase the combination symbol sign. potential for missing important information. 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 Displaying permitted movements provides positive guidance, could ease emphasis on prohibited rather decision load on drivers, and results in fewer last-second decisions in than permitted movements. complex driving conditions. Drivers may be confused about Use overhead lane-use control signs in place of extra turn-prohibition signs; where they can make turn each prohibited movement should be included at least once on turn- movements and where a through prohibition signs. movement is the only permitted movement. 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. More research is needed to better understand severity of these collisions. the effectiveness of many of the countermeasures in terms of collision mitigation and prevention. The findings suggest the need for the following areas of Use of Chapter 10 of the Manual on Uniform Traffic research: Control Devices for Streets and Highways (MUTCD). This research has revealed a variety of countermeasures Success and/or effectiveness of the countermeasures being used by agencies to mitigate collisions between being used by agencies. Transit agencies have taken a LRVs and motor vehicles at signalized intersections; number of approaches and implemented a variety of however, some of the countermeasures being used are countermeasures to mitigate collisions between LRVs not necessarily consistent with those in Chapter 10 of the and motor vehicles at signalized intersections. Although MUTCD. In particular, agencies are using a variety of some of these countermeasures have been more effective train warning signs and no turn signs. More research is than others from the perspective of the agencies, there needed to better understand why agencies do not always have been few empirical studies conducted to examine use the warning and control devices recommended in the the effectiveness of the countermeasures in terms of MUTCD and what impact these inconsistencies have on driver compliance, collision frequency, or collision safety.

OCR for page 33
36 TABLE 6 SCENARIO: MOTORISTS VIOLATE ACTIVE TURN-PROHIBITION SIGNS AND TRAIN-APPROACHING SIGNS IN CONFLICT WITH LRV OPERATION Possible Cause Possible Engineering Countermeasures Active signs may be Use train-activation system to activate train-approaching warning signs. activated too far in advance of arrival of the LRV. Signs may be activated too Use train-activation system to activate train-approaching warning signs. late to provide sufficient advance warning to motorists. Motorists do not understand Install train-approaching warning signs. why the signs are on and/or Install active TRAIN COMING educational plaque below the turn-prohibition why turns are prohibited. signs. Permitting movements at some times and prohibiting Make movement protected-only. them at others causes driver confusion. TABLE 7 SCENARIO: MOTORISTS MAKE LEFT TURNS FROM ADJACENT THROUGH-ONLY LANES INSTEAD OF FROM THE LANES SHARED WITH THE LRVS Possible Cause Possible Engineering Countermeasures Drivers are confused about Use pavement marking arrows indicating allowable movements and ONLY which lane to turn from. (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 8 SCENARIO: DRIVERS ENCROACH UPON OR STOP ON THE TRACKS AND ARE STRUCK BY AN LRV AT A RIGHT ANGLE Issue/Problem Possible Cause Possible Engineering Countermeasures Drivers encroach on or Having too many transverse Reduce the number of transverse lines by stop on the tracks and get markings on the roadway in the using an alternative pattern for crosswalk hit by an LRV at a right vicinity of the intersection (e.g., markings. angle. crosswalk, stop line, railroad Use contrasting pavements on the near and markings) can cause confusion far sides of the stop bar to increase visibility about where to stop. of the stop bar. Where applicable, relocate pavement markings further upstream of the intersection. Motorists may not perceive the Improve the conspicuity of the tracks by LRT tracks crossing the approach using a contrasting pavement treatment. prior to the intersection. Motorists attempt right/left turns If applicable, relocate the stop bar further on red and stop on the tracks to upstream of the intersection. wait for a gap in traffic as the LRV Install crosshatch pavement markings to approaches. designate area where motorists should not be stopped.

OCR for page 33
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 Motorists are unaware an LRV is Install in-roadway lights. indication and collide coming or speed through the Install LRV-activated train-approaching with an LRV at a right intersection in an attempt to beat warning signs on cross-street approach angle. an approaching LRV. (showing side-view/profile of LRV).