Evaluation of Freeway Acceleration Lane Length Adequacy Based on Driving Behavior of Elderly Drivers

Elderly drivers have rapidly grown in the road transportation systems. One of the significant issues associated with elderly drivers is that the performance of perception and reaction contributing to the driving skill and capability is comparatively lower than that of drivers of different ages. In particular, the merging situations frequently occurring at the freeway on-ramp area lead to greater workload for elderly drivers and resultingly higher risk of crash occurrence. From the traffic safety perspective, determining proper acceleration lane length, therefore, is of keen interest because the physical ability of elderly drivers significantly influences whether or not the lane change is safe. This study evaluated acceleration lane length using VISSIM microscopic traffic simulation tool based on the consideration of the increase in elderly drivers. Results showed that approximately 370 meter length is proper in terms of accommodating unsafe merging events at the current rate of elderly drivers, 10%. In addition, it was identified that 415 meter was appropriate under a scenario with 20% of elderly drivers. The outcome of this study would be useful in updating road design guidelines reflecting the characteristics of elderly drivers.