01340648

Component

https://doi.org/10.3141/2254-13

http://scholar.google.com....+Pu&publication_year=2011

Travel time reliability is measured in various ways. Measures used in the transportation engineering field include the 90th or 95th percentile travel time, standard deviation, coefficient of variation, percent of variation, buffer index, planning time index, travel time index, skew statistic, misery index, frequency of congestion, and on-time arrival. Correlations and inconsistencies between these measures were observed on a case-by-case basis in past studies, without a full explanation or examination of the fundamental causes of such differing relationships. This paper analytically examines a number of reliability measures and explores their mathematical relationships and interdependencies. With the assumption of lognormal distributed travel times and the use of percent point function, a subset of reliability measures is expressed in relation to the shape parameter or the scale parameter of the lognormal distribution or to both. This process enables a clear understanding of the quantitative relationships and variation tendencies of different measures. Contrary to some previous studies and recommendations, this paper finds that the coefficient of variation, instead of the standard deviation, is a good proxy for several other reliability measures. The use of the average-based buffer index or average-based failure rate is not always appropriate, especially when travel time distributions are heavily skewed, in which case the median-based buffer index or failure rate is recommended.

01363928

11-2814

English

pp 122-130

2011

Transportation Research Record: Journal of the Transportation Research Board

9780309222990

Print

Figures (2) ; References (24) ; Tables (3)

Mathematical relations; Measurement; Travel time

Coefficient of variation; Interdependencies; Lognormal distribution; Travel time reliability

Highways; Planning and Forecasting; I72: Traffic and Transport Planning

TRIS, TRB

Feb 17 2011 6:18PM

• Behavioral Foundation of Route Choice and Traffic Assignment: Comparison of Principles of User Equilibrium Traffic Assignment Under Different Behavioral Assumptions
• Comparative Analysis of Alternate Econometric Structures for Trip Generation Models
• Congestion Pricing, Heterogeneous Users, and Travel Time Reliability: Multicriterion Dynamic User Equilibrium Model and Efficient Implementation for Large-Scale Networks
• Design Features of Activity-Based Models in Practice: Coordinated Travel–Regional Activity Modeling Platform
• Design of Comprehensive Microsimulator of Household Vehicle Fleet Composition, Utilization, and Evolution
• Dynamic Activity Generation Model Using Competing Hazard Formulation
• Estimating Through-Trip Travel Without External Surveys
• Goodness-of-Fit Evaluation Method for Agent-Based Household Microedata Sets Composed of Generalized Attributes
• Incorporating Stochastic Road Capacity into Day-to-Day Traffic Simulation and Traveler Learning Framework: Model Development and Case Study
• Integrated Equilibrium Travel Demand Model with Nested Logit Structure: Fixed-Point Formulation and Stochastic Analysis
• Investigation of Underlying Distributional Assumption in Nested Logit Model Using Copula-Based Simulation and Numerical Approximation
• Joint Model of Participation In Nonwork Activities and Time-of-Day Choice Set Formation for Workers
• Network User Equilibrium Model for Scheduling Daily Activity Travel Patterns in Congested Networks
• On the Information Matrix in Mixed Logit Models Estimation
• Planning-Constrained Destination Choice in Activity-Based Model: Agent-Based Dynamic Activity Planning and Travel Scheduling
• Properties of Expected Travel Cost Function with Uncertain Travel Time
• Variability of Travel Time, Users’ Uncertainty, and Trip Information: New Approach to Cost–Benefit Analysis