Citation

Turner JM, Dudek CL, Carvell JD. Transp. Res. Rec. 1978; 683: 8-10.

Copyright

(Copyright © 1978, Transportation Research Board, National Research Council, National Academy of Sciences USA, Publisher SAGE Publishing)

DOI

unavailable

PMID

unavailable

Abstract

This paper summarizes four case comparisons designed to evaluate the usefulness of a changeable message signing system to divert vehicles around an incident and to redistribution traffic to available capacity on an alternate route in an effort to reduce motorists' travel time to improve the level of service on the freeway and to enhance safer operating conditions on the freeway by providing motorists with advance information of unusual traffic conditions. Candidate messages for diversion were evaluated by use of two management techniques: diversion of freeway traffic to the service road around the incident, and diversion freeway traffic to arterials around the incident. Measures of effectiveness for candidate messages were derived from two sources: change in diversion rates from natural diversion (nonmanagement) to diversion because of informational signing (management), and the varying candidate messages thereof; and questionnaires, which were distributed to drivers where duration of the incident allowed. In every case comparison exit ramp volumes increased for signed (nonmanaged), natural diversion conditions. The results showed that diversion was greater under a managed condition than under an unmanaged condition. For informational signs only, increases ranged from 125.0 to 324.7 percent for the four case studies. When diversion messages were presented, increases ranged from 147.3 to 343.8 percent. In all cases, exit volumes were greater for diversionary signs than for informational signs. This would indicate a preference by motorists for diversionary information. Downstream entrance ramp volumes also increased under the signed conditions. Increases were greater for diversionary messages than for informational messages; however, in one case, results indicate motorists entered the freeway before they had cleared the blockage.