Citation

Abella RJ, Colony DC, Hansell JD. Transp. Res. Rec. 1976; 596: 3-5.

Copyright

(Copyright © 1976, Transportation Research Board, National Research Council, National Academy of Sciences USA, Publisher SAGE Publishing)

DOI

unavailable

PMID

unavailable

Abstract

A continuous-time semi-Markov highway model can be used to simulate and design highway situations that require a merging manuever. A general continuous-time semi-Markov model can be used to simulate a number of merging situations by the substitution of appropriate values for the design parameters. The substitutions are made into established general formulas. The continuous-time semi-Markov process can then be analyzed with flow graph and Laplace transform techniques. The design parameters included in the model are freeway vehicle headway distributions, lane volumes, lane running speeds, and a gap acceptance function that describes a driver's willingness to accept a given headway in an adjacent lane. The continuous-time semi-Markov model can be used to find the distribution of the time spent by a driver waiting to emerge from an entrance ramp. This distribution can be used to evaluate the freeway entrance ramp designs. The effect of improved visibility on waiting time, for example, could be studied by using the waiting time distribution. Different gap acceptance functions can be used to reflect the effect of improved visibility on a typical driver's merging behavior. The location of a warning that a freeway lane drop is imminent can also be studied by means of a continuous-time semi-Markov model. Design contitions can then be calculated. This proportion can be related to the level-of-service concept. Further work is required before a definitive relation can be established between the output of a semi-Markov model and levels of service as those levels are currently defined.