CVEN 3031: BASE MODEL DEVELOPMENT
The base model development involves the following stages described in the RMS Traffic modelling guidelines: http://www.rta.nsw.gov.au/doingbusinesswithus/downloads/technicalmanuals/modellingguidelines.pdf The following sections relate these concepts with the requirements of the assignment. Model Verification
Verification is achieved by looking at the geometry of the network. It is important to ensure that the model network closely resembles what is observed on site in terms of road widths, lane configuration and location of stop lines. Model Calibration
The assignment guidelines provide the following observed speed data to calibrate the model: “The average free flow speed was found to be 45km/hr”
The idea of calibration is to adjust the model to achieve similar modelled speed results as observed within the field. Free flow speed is the average speed a road user would travel if there were no congestion in normal conditions. The free flow speed occurs when density and flow are equal to zero. Calibration Methodology:
Reduce the inflows to a handful of vehicles (say 5 to 10 from each approach) Use the link evaluation tool to measure the speed of these vehicles as they travel through the roundabout. Determine the average speed across five different seed runs of the model with the above parameters. Adjust the speed distribution, gap acceptance, and driving behaviour characteristics to obtain the 45km/hr average free flow speed.
The assignment guidelines provide the following observed flow data to validate the model: “The Maximum Average Circulating Flow was found to be 950 veh/hr/lane with a standard deviation of 50 veh/hr/lane.” The idea of validation is to adjust the model to achieve similar modelled flow results as observed within the field. What is the Maximum Average Circulating Flow?
If we consider a roundabout which is separated into sections as shown below, the section ij represents the part of...
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