Citation

Munjal PK, Hsu YS, Lawrence RL. Highw. Res. Rec. 1973; 469: 26-39.

Copyright

(Copyright © 1973, National Research Council (U.S.A.), Highway Research Board)

DOI

unavailable

PMID

unavailable

Abstract

Merging of vehicles from on-ramp to freeway is the most likely cause of freeway congestion and disturbance besides geometric bottlenecks and freeway accidents. One of the effective ways to control this type of congestion and disturbance is predicting intervehicular acceptable gap sizes by detectors placed in the shoulder lane at some point upstream of the on-ramp. Vehicles from the controlled-ramp site are released and coordinated to merge into the traffic whenever an acceptable gap is detected. This paper gives the analysis on the prediction of gaps and their associated errors for single- and double-loop detectors. Analtyical expressions for errors in gap prediction and speed estimation were derived and validated against experimental observation obtained from aerial photographic data and were related to different sensing pulse rates and detector locations for single- and double-loop detectors. The problem of gap prediction was also related to the stability of traffic in the vicinity of an on-ramp. The effects of lane changing and variation in speed of the individual car between the detector location and the on-ramp merge point were also analyzed from experimental data. A comparison of fixed-metering strategy and gap-prediction strategy is made, and the fixed-metering rate is determined according to the measured occupancy from the experimental data.

RESULTS indicate that the gap-prediction strategy has great application value.

Language: en

Keywords

HIGHWAY TRAFFIC CONTROL; HIGHWAY ACCIDENTS; AERIAL PHOTOGRAPHY