ACCURATE ESTIMATION OF TRAVEL-TIMES FROM SINGLE-LOOP DETECTORS

Citation
Kf. Petty et al., ACCURATE ESTIMATION OF TRAVEL-TIMES FROM SINGLE-LOOP DETECTORS, Transportation research. Part A, Policy and practice, 32(1), 1998, pp. 1-17
Citations number
11
Categorie Soggetti
Transportation,Transportation
ISSN journal
09658564
Volume
32
Issue
1
Year of publication
1998
Pages
1 - 17
Database
ISI
SICI code
0965-8564(1998)32:1<1:AEOTFS>2.0.ZU;2-0
Abstract
As advanced traveler information systems become increasingly prevalent the importance of accurately estimating link travel times grows. Unfo rtunately, the predominant source of highway traffic information comes from single-loop loop detectors which do not directly measure vehicle speed. The conventional method of estimating speed, and hence travel time, from the single-loop data is to make a common vehicle length ass umption and to use a resulting identity relating density, dow, and spe ed. Hall and Persaud (Transportation Research Record 1232, 9-16, 1989) and Pushkar et al. (Transportation Research Record 1457, 149-157, 199 4) show that these speed estimates are flawed. In this paper we presen t a methodology to estimate link travl times directly from the single- loop loop detector flow and occupancy data without heavy reliance on t he flawed speed calculations. Our methods arise naturally from an intu itive stochastic model of traffic how. We demonstrate by example on da ta collected on I-880 data (Skabardonis et al. Technical Report UCB-IT S-PRR-95-S, Institute of Transportation Studies, University of Califor nia, 1994) that when the loop detector data has a fine resolution (abo ut one second), the single-loop based estimates of travel time can acc urately track the true travel time through many degrees of congestion. Probe vehicle data and double-loop based travel time estimates corrob orate the accuracy of our methods in our examples. (C) 1998 Elsevier S cience Ltd.