LIGHT RAIL PREEMPTION OF TRAFFIC SIGNALS: A QUESTION OF BALANCE

As Maryland expands its network of light rail transit facilities, an increasing number of situations arise where light rail and traffic-signalized intersections must operate in conjunction with each other. These include at-grade crossings close to signalized intersections and light rail facilities that closely parallel arterial roadways where there are closely spaced traffic signals on the arterial. These locations present the traffic engineer with unique problems that must be resolved to facilitate movement of the light rail vehicle and other vehicular traffic through the area. In most cases, the periodic preemption of a traffic signal at an isolated intersection will cause only momentary disruption to vehicular traffic. It is when more frequent preemption occurs, or when the signal operates as part of a coordinated traffic signal system, that problems arise. These include disruption of traffic signal coordination on the arterial, excessive clearance intervals needed to ensure that right-of-way has been cleared for the light rail, and excessive delay to vehicles waiting at the preempted traffic signal. In addition no two locations have the same characteristics or solutions. The traffic engineer must consider these and other factors when developing a traffic control scheme for each individual location. Maryland is evaluating several traffic control strategies for these types of locations. They include allowing the signal to cycle through other nonconflicting phases while the light rail vehicle passes through an intersection; allowing the signal controller to select, on the basis of traffic demand, which phase should be serviced first after preemption; and reducing the disruption to the signal system caused by frequent light rail preemption. The field testing and design of these strategies are addressed.

Language

  • English

Media Info

  • Media Type: Digital/other
  • Features: Figures; Photos;
  • Pagination: p. 285-293
  • Monograph Title: SEVENTH NATIONAL CONFERENCE ON LIGHT RAIL TRANSIT, BALTIMORE, MARYLAND, NOVEMBER 12-15, 1995. VOLUME 1
  • Serial:

Subject/Index Terms

Filing Info

  • Accession Number: 00716789
  • Record Type: Publication
  • ISBN: 0309061520
  • Files: TRIS, TRB
  • Created Date: Jan 30 1996 12:00AM