In order to decrease the simulation runtime the

Info iconThis preview shows page 1. Sign up to view the full content.

View Full Document Right Arrow Icon
This is the end of the preview. Sign up to access the rest of the document.

Unformatted text preview: were gathered from the field data collected. As mentioned earlier, 3 days of data was collected in the field. Figure 14 and Figure 15 shows the hourly vehicle counts for 3 days of data, both for driving and passing lanes. From the 55 graphs it can be easily observed that the daytime hourly vehicle counts are greater than the nighttime counts. In addition, it was observed that the counts for the data collected on 08/20/2004 were greater than the hourly vehicle counts of the other days. The hourly vehicle counts for the day with the maximum number of vehicles per hour 08/20/2004 was selected for the simulation example. The output variables of the simulation model are the queue length and the waiting time at the lane closure taper, and it was expected to be greater for the time periods with high hourly vehicle counts. 800 Number of Vehicles per Hour 700 600 500 400 300 200 100 0 12:00 AM 3:00 AM 6:00 AM 9:00 AM 12:00 PM 3:00 PM 6:00 PM 9:00 PM 12:00 AM Time of the Day Driving Lane (08/20/04) Driving Lane (08/21/04) Driving Lane (08/22/04) Figure 14: Hourly Traffic Counts for Driving Lane for 3 Days of Data 56 800 Number of Vehicles per Hour 700 600 500 400 300 200 100 0 12:00 AM 3:00 AM 6:00 AM 9:00 AM 12:00 PM 3:00 PM 6:00 PM 9:00 PM 12:00 AM Time of the Day Driving Lane (08/20/04) Driving Lane (08/21/04) Driving Lane (08/22/04) Figure 15: Hourly Traffic Counts for Passing Lane for 3 Days of Data In Appendix C adjusted hourly vehicle counts for 08/20/2004 (Friday) daytime data and their corresponding inter-arrival times for given cumulative percentages are presented for driving lane and passing lane. Inter-arrival times for each cumulative percentage values were calculated according to the corrected IAT tables given in Table 8 and Table 9. The IATs for the vehicle counts which are not given in the table were calculated using a linear interpolation. The inter-arrival times and their cumulative percentage values given for each 15 minute interval in Appendix C were entered to the create module of ARENA. Continuous probability distribution function was used for the arrival rates. The inter-arrival times for 57 the vehicles for the create module were entered with the given expression using the interarrival times and their cumulative percentages for corresponding number of vehicles per hour per lane. CONT(0.0001,0.1,0.01,0.71,0.02,0.88,0.05,1.16,0.1,1.54,0.2,2.20,0.3,2.88,0.4,3.6 8,0.5,4.68,0.6,5.93,0.7,7.46,0.8,9.56,0.9,13.25,0.95,16.91,0.98,20.93,0.99,23.57,1,30.23) 3.2.2.1.3 Vehicle Types Vehicles entered to the system as entities and they are transported in the system with guided vehicles transport option of the ARENA simulation program. Two different vehicle types were defined in the ARENA simulation model; passenger cars and trucks. The percentages of trucks and passenger cars were determined using the field data collected. It was assumed that the percentages of trucks and cars remain the same for the 24 hour simulation time period. Using the OU video record data presented in Table 2, the percentages of trucks and cars were determined which are given in Table 14, both f or driving and passing lane. These percentages were assigned to the vehicles at the beginning of the simulation run. 58 Table 14: Percentages of Passenger Cars and Trucks for Driving Lane and Passing Lane according to OU Video Record Percentages Vehicle Type Driving Lane Passing Lane Passenger Car 91% 9% Truck 61% 39% In the simulation model, passenger cars were simulated using the guided vehicle module of ARENA. Vehicle length, acceleration and deceleration rates, speed at the beginning of the simulation can be assigned to this module. The passenger car guided vehicle module variables were adopted from Traffic Engineering Handbook [23]. The default acceleration and deceleration rates of the guided vehicles in ARENA were used for the passenger cars. The lengths of passenger cars in the model were assumed to be 16 feet. In addition to this 16 feet length, 4 feet was added to the length of the passenger cars to prevent the collision of the vehicles in stopped traffic. In the model trucks were also simulated using the guided vehicle module of ARENA. The default acceleration and deceleration rates of the guided vehicles were used in ARENA for the trucks. Trucks in the model were assumed to be 60 feet in the model. In addition to the 60 feet vehicle length, 5 feet was added to the length of the trucks to prevent the collision of the vehicles in stopped traffic. 59 3.2.2.1.4 Speed Profile The speeds of the vehicles were assigned using a probability density function (pdf) at the beginning of the simulation. Different flow speeds were assigned to each vehicle with the function. These speeds were assigned as the desired speeds of the vehicles during simulation. If the vehicles need to decelerate or accelerate according to the conditions of the roadway, the default acceleration and deceleration rates are used in the simulation. Using a pdf for determining the speed profile also allowed us to simulate different driver types. The most commonly used mathematic...
View Full Document

Ask a homework question - tutors are online