Random Effect Models to Predict Operating Speed on Horizontal Curves for Intercity Buses Based on Naturalistic Driving Data

The most common cause of death and injury worldwide is traffic accidents. Several studies have shown that these accidents occur primarily on rural roads, especially those with horizontal curves. Studies have indicated that inconsistency in geometric design is one of the main reasons for this problem. Road geometric consistency refers to the alignment of the road geometry with the expectations of the driver. In evaluating road design consistency, operating speed is the most common criterion, which can be estimated by using operating speed models. Buses account for the majority of passenger movement, so it is important to study their operating speed. In this work, the random effect model is used for ۱۵۰ buses passing through ۶۹۰ horizontal curves of the Tehran-Qaem­­shahr highway to estimate the performance speed in horizontal curves. Among all the highways connecting the northern area of the country to the capital, that expressway was chosen for the study because of many reasons such as the minimum changes in the geometry, high volume of daily bus traffic, various topographic conditions, and the availability of data needed for the study. Besides, the variables of driving time, the geometric design of the curve, the driver's data, and the characteristics of the bus are examined in this study. Finally, the developed model revealed that the average radius of the curve, the volume of traffic, the reverse curves, the percentage of heavy vehicles, the location of fixed speed cameras, the posted speed limit, and the darkness were all significant factors.

Keywords:

Operating speed models , Random Effect Models , Intercity Buses , Four-lane Divided Rural Highway , Horizontal Curves