The distance gap between two vehicles is calculated

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Unformatted text preview: less than MSSLC to avoid collisions. MSSLC includes the probability of emergency braking conditions in order to simulate the real traffic conditions in detail. The researchers calculated the MSSLC for different conditions. In the ARENA simulation model, MSSLC calculated using the assumption that acceleration rates and deceleration rates for the lane changing vehicle, leading vehicle, and following vehicle are the same. The gaps required for lane changing were derived from the figures given below. In Figure 19 the space required for leading vehicle gap is given according to the difference in speeds between the two vehicles. Figure 19: MSSLC for the space between the leading vehicle and the merging vehicle versus relative speed between the lanes (adapted from Kanaris et al. [32]) 65 In Figure 20 the space required for following vehicle gap is given according to the speed differences between two vehicles. Figure 20: MSSLC for the space between the following vehicle and the merging vehicle versus relative speed between the lanes (adapted from Kanaris et al. [32]) The values derived from the graphs were added to the vehicle lengths and the minimum required gaps for lane changing were calculated. Table 16 shows the required distances for the passenger cars and trucks. Required distances for lane changing given in Table 16 are the distances used before the end of the lane. There are no vehicles waiting in the queue for lane changing. The MSSLCs derived from the graphs presented by Kanaris et al. did not match with the field data collected at I-76 Westbound since in real life conditions lane changing does not occur at safe space distances all the time. 66 Table 16: Minimum Safe Space for Lane Changing before the Lane Closure Taper (adapted from Kanaris et al. [32]) Minimum Safe Spacing for Lane Changing (ft) Speed Difference (Speed on Adjacent Lane – Merging Vehicle) (ft/s) Passenger Car Truck Lead Gap Speed Difference < - 50 ft/s - 50 <Speed Difference <= -35 ft/s - 35 <Speed Difference <= -15 ft/s - 15 <Speed Difference <= 15 ft/s 15 < Speed Difference <= 35 ft/s 35 < Speed Difference <= 50 ft/s 50 < Speed Difference Vehicle Length Lag Gap Total Vehicle Length Total 200 ft 20 ft 850 ft 1070 ft 65 ft 1115 ft 160 ft 20 ft 540 ft 720 ft 65 ft 765 ft 100 ft 20 ft 450 ft 570 ft 65 ft 615 ft 20 ft 20 ft 180 ft 220 ft 65 ft 265 ft 20 ft 20 ft 130 ft 170 ft 65 ft 215 ft 20 ft 20 ft 80 ft 120 ft 65 ft 165 ft 20 ft 20 ft 30 ft 70 ft 65 ft 115 ft Rakha and Crowther [33] compared three most known car following models in the literature; Greenshields, Pipes, and Van Aerde car following models. Greenshields is a single regime macroscopic car following model which uses two parameters for determining the car following distance. Free speed and the capacity or the jam density is used for determining the car following distances in this model. Pipes car following model is a two regime microscopic model, which uses the free speed, jam density, and driver sensitivity factor. Van Aerde car following model uses four parameters; free speed, speed at capacity, jam density, and capacity. The authors compared these 3 car following 67 models and then compared the Van Aerde model’s results with the real world data. It is shown that the Van Aerde car following model gives the best fitting distribution to the real headway distance data. In Figure 21, comparison of Van Aerde car following model with the field data is given. In Figure 22, the comparison of three models fitting distributions are given. Figure 21: Comparison of the Van Aerde Car Following Model with the Field Data (adapted from Rakha and Crowther [33]) 68 Figure 22: Comparison of Greenshields, Pipes, and Van Aerde Car Following Models (adapted from Rakha and Crowther [33]) Using Figure 21, comparison of Van Aerde model with the field data graphs, required gaps for lane changing were generated. Required gaps are given in Table 17. The speeds of the leading vehicle, following vehicle, and the merging vehicle are assumed to be the same. 69 Table 17: Required Gaps for Lane Changing Maneuver Derived from Van Aerde Car Following Model (adapted from Rakha and Crowther [33]) Required Gaps for Lane Changing (ft) Speed Passenger Car Truck Lead Gap Vehicle Length Lag Gap Total Vehicle Length Total Speed <= 10 ft/s 40 ft 20 ft 40 ft 100 ft 65 ft 150 ft 10 ft/s <Speed <= 35 ft/s 65 ft 20 ft 65 ft 150 ft 65 ft 200 ft 35 ft/s <Speed <= 55 ft/s 100 ft 20 ft 100 ft 225 ft 65 ft 275 ft 55 ft/s <Speed <= 75 ft/s 130 ft 20 ft 130 ft 275 ft 65 ft 325 ft 75 ft/s < Speed 165 ft 20 ft 165 ft 350 ft 65 ft 400 ft Lane changing behavior is one of the most important features of a traffic simulation model. There are two types of lane changing behavior in microscopic traffic simulation; mandatory and discretionary lane changing behaviors. Mandatory lane changing is defined as changing the lane when there is a termination of lane. When there is a termination of the lane, the vehi...
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