Car Drivers’ Experienced Level of Service on Freeways

Søren Underlien Jensen, TRB Annual Meeting, 2017

The Danish Road Directorate sponsored a study to develop methods for quantifying car drivers experienced level of service on freeways (CLOS). The results provide a measure of how well freeways accommodate car travel.

In order to determine how traffic operations, geometric conditions, and other variables affect car drivers' satisfaction, 188 randomly selected respondents were shown 80 video clips of roadway segments filmed from a driving passenger car. Video clips consist of high resolution video filmed through windshield, side windows including exterior mirrors and rear window. Video clips also include a GPS based speedometer.

Respondents rated video clips on a six-point scale ranging from very satisfied to very dissatisfied. This resulted in 7,497 useable ratings. 400-450 variables describe respondent answers to six background questions and the video clips i.e. roadway segment geometries, traffic operations, surroundings, weather, etc.

Car driver satisfaction models were developed using cumulative logit regression and ordinary generalized linear modeling. The six presented models include 3-10 variables, which relate significantly (p ≤ 0.05) to satisfaction ratings. These variables are average speed, speed limit, width of hard shoulder, number of entries and other merge areas per mile, number of exits and other diverge areas per mile, flow of long vehicles per lane per hour, direction of sunlight, drivers age, type of driver's license, and drivers yearly mileage. Models return percentage splits of the six levels of satisfaction or average satisfaction. These splits or averages are transformed into a level of service (LOS).

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