I was trying to model a freeway entrance in Vissim do some "variable speed limit" comparison experiments.
in "scenario 1", I set up the Vehicle Input with 8 time intervals(0-600,600-1200,1200-1800,1800-2400,2400-3000,3000-3600,3600-4200,4200-4800).
in "scenario 2", I set up the "Vehicle Input" with 6 time intervals(0-600,600-1200,1200-1800,1800-2400,2400-3000,3000-3600).
In both scenarios, the volume is the same for all time intervals (700veh/h), and same random seed for both scenarios.
I found out that the real-time volume from the freeway ramp is different between two scenarios when I check out the .mes file(I set up the data collection point at the upstream of the freeway ramp and there is no congestion):
This surprised me, I thought that as long as the "random seed" is the same, the vehicle will follow the same "arrival mode" in the simulation so that the real-time volume should be same.
Several factors can affect real-time volume during simulation in Vissim, including input parameters, simulation settings, and model complexity. In your case, differences in real-time volume between scenarios could be influenced by the number and timing of vehicle inputs, variations in traffic flow due to lane changes or merging behavior, and the simulation environment's stochastic nature. While maintaining the same random seed helps ensure reproducibility, small variations in vehicle behavior and interactions can still occur, especially with changes in input configuration or simulation duration. Additionally, subtle differences in model setup or traffic dynamics might amplify over time, leading to variations in real-time volume. To investigate further, consider examining specific simulation outputs, such as vehicle trajectories and queue lengths, and adjusting input parameters or model settings to minimize discrepancies between scenarios.