Empirical Evaluation of Lane Changing Following Gap Distance on Expressway

Abstract

Abstract Lane changing (LC) is an essential aspect of driving behaviour on expressways, which impacts on traffic efficiency and safety. Therefore, a wrongful execution of LC, especially the wrong choice following distance before the LC manoeuvre. This could lead to road crashes, mostly in the form of rear-end, sideswipe, or angled crash. This research assesses the characteristics of drivers’ following gap distance during LC. The study was performed on a segment along Kuala Lumpur – Seremban expressway. Data were collected along the selected segment using an instrumented test vehicle approach. A passenger car was instrumented with a Video Velocity Box (VBox), which an on-board data acquisition system used for video recording of field traffic events. Hence, VBox attached to the test vehicle was used for recording the following gap distance during LC manoeuvres in the field. After that, the video records were played back on a computer to estimate the gap distance. A total of 174 following incidences were observed in this work. Finding from the study revealed that the following gap distance before LC of the sampled motorists ranges from 4.89 to 81.15 m with a mean and standard deviation of 18.47 and 12.16 m, respectively. Furthermore, out of the 174 sampled drivers, about 86.7% recorded following gap distances in the range of 10 to 30 m, implying that the majority of the motorists accept short gaps while executing LC. It was also found that the space gap is regarded as an essential variable than the time gap because as drivers travel at desired speeds, they tend to be guided by the available space rather than time.