01047317

Component

The estimation of path or trip travel-time reliability is critical to any Advanced Traveler Information System. The state-of-practice procedures for estimating path travel-time reliability assume that travel times follow a normal distribution and require a measure of trip travel-time variance. The study analyzes AVI data from San Antonio and demonstrates through goodness-of-fit tests that the assumption of normality is, from a theoretical standpoint, inconsistent with field travel-time observations and that a lognormal distribution is more representative of roadway travel times. However, visual inspection of the data demonstrates that the normality assumption may be sufficient from a practical standpoint given its computational simplicity. The paper then proposes five methods for the estimation of path travel-time variance from its component segment travel-time variances. The analysis demonstrates that computing the trip travel-time coefficient of variation as the conditional expectation over all realizations of roadway segments provides estimates within 13% of field observations for both uncongested and congested conditions.

01042056

07-0488

English

15p

2007

Transportation Research Board 86th Annual Meeting

CD-ROM

Figures (8) ; References (10) ; Tables (3)

Advanced traveler information systems; Analysis of variance; Automatic vehicle identification; Highway operations; Reliability; State of the practice; Traffic; Traffic congestion; Traffic data; Traffic flow; Transportation planning; Travel time

San Antonio (Texas)

Data and Information Technology; Highways; Operations and Traffic Management; Planning and Forecasting; I72: Traffic and Transport Planning

Transportation Research Board Annual Meeting 2007 Paper #07-0488

TRIS, TRB

Feb 8 2007 5:04PM