دانلود رایگان مقاله ارزیابی اثرات مکانی و زمانی تصادف بر بزرگراه با شبیه سازی ترافیک

Abstract

The focus of this paper is to simulate, evaluate and assess spatial and temporal effects in travel time variation and upstream distance or length of upstream links affected due to a crash. Traffic simulations were conducted for different conditions in VISSIM 5.30™ to obtain travel times at various points upstream of the crash location, over time, along a freeway corridor. Travel time variation between fatal crash condition and no crash condition (baseline condition) and between injury crash condition and no crash condition (baseline condition) were computed and compared to evaluate the effect of a crash on a freeway. Results obtained showed that fatal crash on freeways has an effect under low, moderate, and high traffic volume conditions, whereas injury crash has an effect only under moderate and high traffic volume conditions. The travel time variation and upstream distance affected due to a fatal crash on the right-most lane was generally higher than fatal crash on the left-most lane. The trends remained fairly consistent irrespective of the lane on which an injury crash occurred. The upstream distance affected due to a fatal crash varied from 1.5 miles to ∼7.5 miles based on traffic volume and lane on which the fatal crash occurred. It varied from ∼0.5 miles to 7 miles due to an injury crash and traffic condition. Queue may start dissipating at least 15 min after blocked lanes are re-opened for normal traffic flow depending on the type of crash, traffic volume and lane in which the crash occurred. The results and findings from this research can be applied to emulate dynamic message signs over time and space so as to alert the motorists about the length and duration of congestion depending on the severity of crash and lane on which the crash occurred.

5. Conclusions

An evaluation and assessment of travel time variation and upstream distance affected due to a fatal or injury crash on a freeway corridor is presented in this paper. Observations from simulations show that fatal crash on freeways has an effect under low, moderate and high traffic volume conditions, whereas injury crash has an effect only under moderate and high traffic volume conditions. The relative variation in travel time is higher for moderate traffic volume or uncongested conditions than when compared to high traffic volume or congested conditions. Therefore, it can be concluded that non-recurring congestion plays a vital role along with recurring congestion and should be taken into account to quantify overall congestion. Non-recurring congestion measures when combined with recurring congestion measures will increase the reliability in assessing the congestion levels for a road network. Hence, incorporating the effect of a crash on travel time variation, when assessing the reliability of road network, will result in application of a better performance measure for quantifying congestion. The travel time variation and upstream distance affected due to a fatal crash on the right-most lane is generally greater than a fatal crash on the left-most lane. The trends are fairly consistent irrespective of the lane on which an injury crash occurred. The maximum upstream distance affected due to a fatal crash is
1.5 miles over time when traffic volume is 1000 vph, whereas it is
7.5 miles over time when traffic volume is 3000 vph or 6000 vph. In case of an injury crash, the upstream distance affected is
0.5 miles, 2 miles and
7.5 miles over time when traffic volume is 1000 vph, 3000 vph and 6000 vph, respectively.