The Highway Capacity and Quality of Service Committee of TRB, which oversees the development of the Highway Capacity Manual, has formally recognized a need to improve the current level-of-service (LOS) methodologies. Among the concerns about the methodologies is the extent to which LOS estimates correspond to road users' perceptions. In recognition of these concerns, the objectives of this study were to ( a) develop and test a methodology to obtain drivers' opinions with regard to urban street quality of service (QOS), ( b) apply the methodology to identify the factors that affect drivers' perceptions of QOS on urban streets, and ( c) provide a qualitative foundation for the development of quantitative QOS tools that are based on the perceptions of drivers. This study used an in-vehicle field approach to determine the factors that affect automobile drivers' perceptions of service quality on urban streets. While driving on a preselected route, 22 participants in four cities were asked to speak aloud about their driving experience and the factors that influenced their perception of service quality. Afterward, drivers also completed a written questionnaire. The drivers expressed their opinions about a wide range of issues, including simple observations, more detailed evaluations, and broad concerns related to the roadway environment. From the drivers' comments, 40 factors were identified as relevant to their perception of service quality on urban streets. The authors believe that by identifying a wide range of factors that influence drivers' perceptions of service quality on urban streets, this study has increased the knowledge and understanding of the needs and values of automobile drivers on urban streets and has laid the groundwork for future studies aimed at developing quantitative QOS tools and models.
The purpose of the study reported here was to examine whether age and spatial ability are factors that influence a driver' s ability to navigate and to use navigational displays. These factors were examined because previous research suggests that spatial ability may underlie navigational performance, including route-following and mapreading, and that these skills may diminish with age. Thus, older drivers and drivers with weak navigational skills, may have a heightened need for, and be particularly served by, in-vehicle route guidance displays found in Advanced Traveler Information Systems (ATIS).A total of 56 drivers were tested on spatial ability. The drivers then performed a navigational task in a part-task driving simulator using different navigational aids, including: (1) text directions, (2) an enlarged, mounted paper map, (3) a standard-scale paper map, and (4) a turn-by-turn route guidance ATIS display. The major findings were that: (1) older drivers showed worse navigational performance than younger drivers, (2) the worse performance found in the older group was attributable to their lower spatial ability, (3) spatial ability predicted navigational performance, and (4) a simulated ATIS turn-by-turn display enhanced navigational performance. The implications of the results are that navigational ability declines with age due to decrements in spatial ability and perceptual speed, and ATIS route guidance has the potential to facilitate navigational performance in drivers of varying spatial abilities and age.
This paper presents the results of a study that compared drivers’ assessments of the performance of urban streets with objective measures of performance, including level of service (LOS). The purpose of the study was to test the ability of LOS to predict drivers’ perceptions of service quality. Seventy-seven automobile drivers rated the service quality of half-mile segments of urban streets as depicted on videotaped scenes from the driver's perspective. Drivers rated 12 to 15 video segments on a six-point scale from very satisfactory to very unsatisfactory. After rating all segments, the drivers selected and ranked from a list of 36 factors the three factors that they considered the most important to quality. The results show that the mean driver rating had statistically significant correlations with operational and design characteristics and aesthetics, including the following variables: travel time, average travel speed, number of stops, delay, number of signals, lane width, the presence of trees, and the quality of the landscaping. LOS, calculated by the Highway Capacity Manual methodology, predicted 35% of the variance in mean driver rating. This finding suggests that LOS does not completely represent drivers’ assessments of performance because drivers perceive the quality of urban street segments in several dimensions, including travel efficiency, sense of safety, and aesthetics.
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