Car Drivers’ Experienced Level of Service on Freeways

Abstract

The Danish Road Directorate sponsored a study to develop methods for quantifying car drivers’ experienced level of service on freeways. The results provide a measure of how well freeways accommodate car travel. 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 driven passenger car. Video clips consisted of high-resolution video filmed through a windshield, side windows including exterior mirrors, and a rear window. Video clips also included a GPS-based speedometer. Respondents rated video clips on a six-point scale ranging from very satisfied to very dissatisfied. The result was 7,497 usable ratings. Four hundred to 450 variables described respondents’ answers to six background questions and the video clips, that is, roadway segment geometries, traffic operations, surroundings, weather, and so forth. Car driver satisfaction models were developed with cumulative logit regression and ordinary generalized linear modeling. The six presented models included three to 10 variables, which related significantly ( p ≤ .05) to satisfaction ratings. These variables were 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, driver age, type of driver’s license, and driver yearly mileage. Models returned percentage splits of the six levels of satisfaction or average satisfaction. These splits or averages were transformed into a level of service.