Lexicon for Conveying Travel Time Reliability Information

Abstract

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It’s a Matter of Time: Assessment of Additional Time Budgeted for Commuting to McGill University Across Modes

“…An abundance of research has emerged that provides an assortment of mathematical calculations to determine travel time reliability; however, there is no consensus within the transportation profession as to what the appropriate measures should be (18,26). Here, an example of a simple measure that is most relevant to this study is explained briefly.…”

“…The buffer index is analogous to the concept of a safety margin presented by Knight, referring to the extra time people add to their average travel duration to reduce the effects of unexpected delays and to ensure prompt arrival at their destination (4). The buffer index is calculated as the difference between the 95th percentile of travel time and the average (mean or median) travel time divided by the average travel time; it is conveyed as a percentage in which travel time reliability decreases with higher values (26). For example, a buffer index of 30% would indicate that the commuter should allocate 9 additional minutes for a 30-min trip, whereas a buffer index of 40% would indicate that an allocation of 12 additional minutes for travel is recommended.…”

“…For example, a buffer index of 30% would indicate that the commuter should allocate 9 additional minutes for a 30-min trip, whereas a buffer index of 40% would indicate that an allocation of 12 additional minutes for travel is recommended. Typically, these types of measures, which are mode-specific, require day-to-day data in order in capture the daily variations in travel time and can be used to evaluate the effectiveness of policies (26). For instance, Chen et al assessed the impacts of using real-time information instead of historical data to alert drivers of traffic conditions at five locations on freeways in San Diego, California, and found reductions of buffer time ranging from 7% to 31% (27).…”