Figure 2 The logic used for freeway vehicle simulation
Related Figures (14)
Figure 4. Typical proposed freeway segment cross section The off-ramp geometry is assumed to consist of one lane This configuration allows for movement of raw of vehicles in the highway exit direction. During the simulation model input stage, the user should specify a number equal to (1) to represent the number of off-ramp lanes. The off-ramp lane is assumed to meet the highway link at the end of the deceleration lane. The segment length computation starts from the vehicle generation point (origin point) which includes the followings: Table 2. Parameters of normal acceleration rate Table 1. Default vehicle type proportions Figure 7. VISSIM schematic of proposed site Proposed weaving sections were specified to be examined under different vehicle parameters and various flow conditions with different weaving area configurations. The following is an example for one of the proposed sections explaining how the simulation model was analytically validated. The objective of this test is to examine the model performance by simulating the behavior of traffic stream through a weaving section and The geometric layout of the proposed weaving section and the percentage of the weaving flow are shown in the Figures (5) and (6) respectively. The weaving segment capacity was 4380 veh/h as computed by HCS2000 program for the same prevailing conditions. Figure 5. The geometric layout of the weaving section Figure 6. the flow-weaving diagram The average desired speed of vehicles in the weaving section was chosen to be the measure of effectiveness parameter to compare the results. Figures (7) shows the VISSIM schematic of test site. Table 3. Different categories with their vehicle movement type. Computer programs were used as an aid tools to collect and abstract data from videotape. Their outputs were processed and analyzed to compute average vehicle TT for the different categories. The observed traffic parameter values were specified to the simulation model as an input. Table (4) shows these observed parameters with their statistical values. The observed passenger car percentage Figure 9. FWASIM traffic attribute input The desired speed FWASIM simulation results are compared with that resulted by VISSIM. Figures (8) illustrates and compares the results with the corresponding traffic volume starting from 500 veh/h to the determined section’s capacity. Table 4. Statistical values for observed input parameters The simulation model was run several times with the Table 5. Observed and simulated values of TT Figure 10. Part A to D Comparison between observed and simulated TT for all movement type
