Demo - Vehicle Arrival - Negative Exponential Distribution
Input - 900 vph, 0.25 veh/second or 1 vehicle every 4 seconds
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Summary - Vehicle Inputs - Stochastic vs Exact
Tested using VISSIM 9.0 pack 6 64 bit on Windows 7, default traffic composition: 98% Car - 2% HGV
Tested under well below saturation, near saturation, and exceeding saturation flows by 900, 1800, 2400 vehicles per hour respectively
Time of entry depends on Seed#, Input ID#, Input Type, of course volumes
I tried to replicate VISSIM stochastic arrivals by negative exponential distributions using Mersenne Twister 19937 algorithm as shown in this web demo, however no success after exhausting all random seeds [up to 2,147,483,647 ], if someone did, please let me know
Simulation resolution does not affect number of vehicles entered much, but does affect time of entries
For Stochastic inputs, with volume increases, the variation of number of entering vehicles also increases, but plateaus near capacity and decreases again - as shown inputs from 900 to 1800 to 2400, the standard deviation [10 steps/second] changes from 30.6 to 42 to 20.4
For Exact inputs, the variation generally increases with volumes
