Measuring horizontal curve vehicle trajectories and speed profiles: Pneumatic road tube and video methods

Horizontal curves present drivers with numerous tasks that, if not performed while approaching and negotiating the curve, may result in a roadway departure crash. A vehicle's lateral position within the lane and its speed are two indicators of interest from safety and operational perspectives. These can and have been measured simultaneously at multiple locations along the curve. However, researchers face the challenge of collecting operational data while minimizing impacts on driver behavior, and developing robust, efficient, and accurate means to obtain the data. This paper presents the findings of a series of pilot studies on closed and open courses that investigated the effectiveness and accuracy of pneumatic road tubes and digital video cameras for collecting such data. Closed-course studies investigated a single data collection station setup, whereas an open-course study investigated multiple data collection stations on a horizontal curve. The data were reduced manually and automatically, and tests were performed to evaluate the statistical significance of the results. In general, the pilot studies show that pneumatic road tubes provide a higher level of accuracy than video data. Other findings include that drivers moved towards the centerline of the roadway overall and even more so when the presence of video equipment. It was also found that vehicle mean speeds at the center of the curve were lower with an increase amount of data site-based vehicle data collection equipment present.