Palekar, Trishul Ajit (2006-08). Signal optimization at isolated intersections using pre-signals. Master's Thesis. Thesis uri icon

abstract

  • This research proposes a new signal operation strategy aimed at efficient utilization of green time by cutting down on the start up and response loss times. The idea is to have a "pre-signal" on each main approach a few hundred feet upstream of the intersection in addition to the main intersection signal, which is coordinated with the pre-signal. The offset between the main and pre-signal ensures that the majority of start up losses does not occur at the main signal. The benefits of the system under various traffic conditions were evaluated based on analysis of the queue discharge process and Corridor Simulation (CORSIM) study. The proposed measure should reduce the travel time and total control delay for the signalized network. To attain the objective the following two studies were undertaken: 1. Development of a queue discharge model to investigate the expected benefits of the system. 2. Simulation of the system: In the second part of the research, the proposed strategy was tested using CORSIM to evaluate its performance vis-??? -vis the baseline case. The queue discharge model (QDM) was found to be linear in nature in contrast to prior expectations. The model was used to quantify the benefits obtained from the pre-signal system. The result of this analysis indicated that the proposed strategy would yield significant travel time savings and reductions in total control delay. In addition to the QDM analysis, CORSIM simulations were used to code various hypothetical scenarios to test the concept under various constraints and limitations. As per expectations, it was found that the system was beneficial for high demand levels and longer offsets. The upper limit on offsets was determined by visual observation of platoon dispersion and therefore the maximum offset distance was restricted to 450 feet. For scenarios where split phasing was used, the break even point in terms of demand level was found to be 2500 vph on a three lane approach, whereas that for a lag-lag type of phasing strategy was found to be 1800 vph, also on a three lane approach.
  • This research proposes a new signal operation strategy aimed at efficient utilization of
    green time by cutting down on the start up and response loss times. The idea is to have a
    "pre-signal" on each main approach a few hundred feet upstream of the intersection in
    addition to the main intersection signal, which is coordinated with the pre-signal. The
    offset between the main and pre-signal ensures that the majority of start up losses does
    not occur at the main signal. The benefits of the system under various traffic conditions
    were evaluated based on analysis of the queue discharge process and Corridor
    Simulation (CORSIM) study. The proposed measure should reduce the travel time and
    total control delay for the signalized network.
    To attain the objective the following two studies were undertaken:
    1. Development of a queue discharge model to investigate the expected benefits of
    the system.
    2. Simulation of the system: In the second part of the research, the proposed
    strategy was tested using CORSIM to evaluate its performance vis-??? -vis the
    baseline case.
    The queue discharge model (QDM) was found to be linear in nature in contrast to prior
    expectations. The model was used to quantify the benefits obtained from the pre-signal
    system. The result of this analysis indicated that the proposed strategy would yield
    significant travel time savings and reductions in total control delay. In addition to the QDM analysis, CORSIM simulations were used to code various
    hypothetical scenarios to test the concept under various constraints and limitations. As
    per expectations, it was found that the system was beneficial for high demand levels and
    longer offsets. The upper limit on offsets was determined by visual observation of
    platoon dispersion and therefore the maximum offset distance was restricted to 450 feet.
    For scenarios where split phasing was used, the break even point in terms of demand
    level was found to be 2500 vph on a three lane approach, whereas that for a lag-lag type
    of phasing strategy was found to be 1800 vph, also on a three lane approach.

publication date

  • August 2006