Because of the potential for serious train-vehicle accidents at or near railroad-highway grade crossings, preemption of traffic signals is a very important supplement to an active warning system. Preemption is the transfer of normal signal phasing to a special control mode with the purpose of clearing any vehicles that are queued within the dynamic envelope as the train approaches, and prohibiting signal phases that would allow additional vehicles in the track area while the train is present.
The focus of this research was the determination of the Clear Track Green Interval (or the Queue Clearance Time). The clear track green interval is the most important component of the preemption process because this is the time allotted to clear any vehicles that are queued within the track dynamic envelope. The estimation of the amount of time needed for the Clear Track Green Interval is often left to the discretion of the traffic engineer. To date, the Louisiana Department of Transportation and Development has no explicit guidelines for the traffic engineers in their design of railroad preemption for traffic signals.
This research describes the evaluation of three methodologies that can be used to acquire the clear track green interval for an intersection. The study provides a comparison of the calculated values versus the field (or observed) values with the objective being to show if the calculated times are adequate or if they provide too much time for the action thereby causing adverse affects to the intersection. The second objective of this research is to provide guidance to the traffic engineers in the design of railroad preemption for traffic signals.
Based on the results and analysis of this research, the field observed method yielded a lower clear track green interval 71% of the time. Out of the remaining two methods, the Marshall/Berg method yielded lower results 29% of the time and the Northwestern method always yielded a longer time because of its conservative approach. The instances when the Marshall/Berg method yielded lower results has varying causes. The reasons included: intersections where the side approaches shared the phasing causing the track side approach to have to compete with the other approach to move beyond the track, red light runners causing the drivers to hesitate before proceeding out into the intersection, and geometry issues.
| Identifer | oai:union.ndltd.org:LSU/oai:etd.lsu.edu:etd-04142004-120201 |
| Date | 15 April 2004 |
| Creators | Kenon, DeeAngela Renee |
| Contributors | Chestor Wilmot, Brian Wolshon, Sherif Ishak |
| Publisher | LSU |
| Source Sets | Louisiana State University |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | http://etd.lsu.edu/docs/available/etd-04142004-120201/ |
| Rights | unrestricted, I hereby certify that, if appropriate, I have obtained and attached hereto a written permission statement from the owner(s) of each third party copyrighted matter to be included in my thesis, dissertation, or project report, allowing distribution as specified below. I certify that the version I submitted is the same as that approved by my advisory committee. I hereby grant to LSU or its agents the non-exclusive license to archive and make accessible, under the conditions specified below, my thesis, dissertation, or project report in whole or in part in all forms of media, now or hereafter known. I retain all other ownership rights to the copyright of the thesis, dissertation or project report. I also retain the right to use in future works (such as articles or books) all or part of this thesis, dissertation, or project report. |
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