Speed Transition Zone Design Based on Driving Simulator

Speed transition zone is needed to provide a smooth speed change between two highway segments with very different speed limits. Carelessly or improperly installed speed zone can mislead drivers and create safety problems. The purpose of this study is to establish a design procedure for transitional speed zone on two-lane roadway based on the study with vehicle simulator In order to evaluate the effect of speed limit zone on drivers’ deceleration behaviors when passing different speed zones, two factors were considered in this study, i.e., existence of work zone and horizon curve. The speed gaps in this experiment are 50 km/h (from 80km/h speed zone to 30km/h speed zone) in work zone area and 20 km/h (from 80km/h speed zone to 60km/h speed zone), respectively. By using randomly selected drivers, the study measured driver’s actions in a real vehicle under the simulated environment traveling between speed zones and information was collected at a 0.03 second intervals. Several different measures of effectiveness were used to compare characteristics of the speed distributions, including average speed, 85th percentile speed, and pace speed. Results show that there is a significant difference in speed choice for deceleration between two scenarios due to speed reduction. Relationship between speed limit reduction and deceleration length was described by a linear model. Length of deceleration section was estimated by the model. Results show that the deceleration section is positive relation to speed reduction. The modeling process gives a detailed guidance for design of transitional speed zone.