Freeway travel time reliability maps, using the shape of the day-to-day travel time distribution

Research output: Chapter in Book/Conference proceedings/Edited volumeConference contributionScientific


Reliability of travel times in transportation systems and particularly freeway networks has gained considerable interest in the past decade. In this paper we present two measures for travel time reliability which could be exploited by both researchers and practitioners. Since day-to-day variability of route travel times freeway corridors is generally considered closely related to the reliability of a road network, we argue that both skew and width of the day-to-day distribution of route travel times are relevant indicators for unreliability. Consequently, we propose two reliability measures, based on three characteristic percentiles, that is, the 10th, 50th and 90th percentile for a given route and time of day (TOD) and day of the week (DOW) period. High values of either measure indicate high travel time unreliability. However, the weight of each measure on travel time reliability may be application or context specific. The practical value of these particular measures amongst other things that they can be used to construct so-called reliability maps, which visualize not only the unreliability of travel times for a given DOW/TOD period, but also help identify DOW/TOD periods in which it is likely that congestion sets in (or dissolves). This means identifying the uncertainty of start, end and hence length of morning and afternoon peak hours. Also, the measures may be used in discrete choice models as explanatory variables for driver uncertainty.
Original languageUndefined/Unknown
Title of host publicationTRAIL Conference Proceedings, selected papers
EditorsPHL Bovy
Place of PublicationRotterdam
PublisherTRAIL Research School
Number of pages19
ISBN (Print)90-407-2555-1
Publication statusPublished - 2004
Event8th TRAIL Congress 2004 - Rotterdam
Duration: 19 Nov 200423 Nov 2004

Publication series

PublisherTRAIL research School


Conference8th TRAIL Congress 2004

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  • Conf.proc. > 3 pag

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