PURPOSES : This study defines travel time reliability as a concept that explains the change in travel time that passengers can hardly predict and calculates the value of travel time reliability based on travel objectives. METHODS : Because the reliability of passage time is difficult to estimate from actual passenger data, standard quantification measures have not been established despite various interests. In this study, the reliability of transit time was defined as the expense that passengers did not recognize in advance, such as an accidental delay caused by unforeseen circumstances. For analysis based on the individual behavior of users, the data were constructed using the optional experiment method (marginal rate of substitution method) of the stated preference survey, which has the advantage of controlling the correlation between attribute variables and maintaining the independence of the data of the study. RESULTS : Consequently, the reliability value of travel time in mandatory-purposed traffic was almost identical to the value of travel time, and the reliability value of travel time in return and shopping/leisure, which is not mandatory during non-business-purpose traffic, is lower than the value of travel time. Comparing and analyzing with existing studies on estimating the reliability value of transit time, both work/ non-work purposes are in line with the overall research results. CONCLUSIONS : Estimating the reliability value of transit time for each purpose of passage was the first attempt, and it is meaningful to suggest a direction for quantifying and applying the reliability value of transit time along with the passage time value of this study.

PURPOSES : Benefits for improvement of travel time reliability obtained from construction of new highways should be considered as a major factor in the feasibility study for highway constructions. The purpose of this study is to develop a method of estimation for the value of travel time reliability. METHODS : Highway type (urban/rural highway) and traffic flow type(interrupted/uninterrupted) was considered to estimate he value of travel time reliability. And Double-bounded Dichotomous Choice among Contingent Valuation Method(CVM) was applied to survey the willingness-to-pay of drivers when travel time reliability is improved. Finally the value of travel time reliability was estimated using the results of survey and logit model. The value of travel time reliability was estimated considering travel objectives, time constraint travel and non-time constraint travel. RESULTS: The value of travel time reliability of business trip is higher than that of non-business trip. The value of travel time reliability of time constraint travel is higher than that of non-time constraint travel. The value of travel time reliability in urban area is higher than that in rural area. CONCLUSIONS: It was concluded that the proposed method in this study is more realistic and proper to estimate the value of travel time reliability because it reflects the situations of time constraint travel and non-time constraint travel.