Tutorial Lane Occupancy

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Link Density

Lane Occupancy is the ratio of sum of the lengths of the vehicles to the length of the road section in which those vehicles are present.

Link Density Link Density is calculated by $$ \frac {v} {S} $$.

where,


 * 'v' is Flow Rate in analysis direction in vehicle per mile per lane (veh/mi/ln)
 * 'S' is Average Speed in miles per hour(mi/hr)

Calculation and Analysis


 * Run Simulation in SwashSim for the freeway network.
 * Consider warm-up time and simulation time as suitable. (For this case 300 seconds and 900 seconds have been considered as warm up time and simulation time).
 * Link Density is calculated from the Link Results.csv output file and Time Step Data (TSD) file.
 * For Flow rate, first filter the data in the TSD file by excluding vehicles that enter the link before warm-up time.
 * Also filter out those vehicles that are still on the link after the simulation time ends.
 * After filtering, the total number of vehicles in the 'TSD' file should be equal to the total number of vehicles in the 'Link Results.csv' file (Column U).
 * Calculate Flow Rate in vehicles per hour per lane using total number of vehicle.
 * Calculate Link Density using Flow rate and average speed (Link Results File, column F).

Detector Occupancy

Detector Occupancy is measured as the percentage of time for which a detector is occupied (To) by a vehicle relative to the total observation time (T).

Calculation and Analysis


 * Add Detectors at suitable distance to each lane of the link to be analyzed.
 * Run Simulation in SwashSim for the freeway network.
 * Link_ID#_Lane_ID#_Detector_ID# output file is used to calculate the (To).
 * (To) is the summation of difference of actuation 'time off' and actuation 'time on' for all the vehicles after the warm-up time.
 * T is the simulation duration in seconds.
 * Divide (To) by T and multiply by 100
 * Compare calculated value to that in DetectorAggregateMeasures file (Column N).
 * Estimated Density is ratio of Detector Occupancy and Effective Length (in feet per mile).