22 daytime passing lane n162 average1399 sec standard

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Unformatted text preview: 10000 1000 Nighttime-Passing Lane N=124 Average=135.04 sec Standard Deviation=229.16 sec Minimum=7.84 sec Maximum=1620.15 sec 100 10 1 0 100 200 300 400 500 600 700 Average Interarrival Time (sec) Daytime-Passing Lane Nighttime-Passing Lane Figure 5: Comparison of Average Inter-arrival Times versus Number of Vehicles per Hour for Daytime and Nighttime Passing Lane Data As mentioned earlier, the traffic was videotaped with a time-stamped video. Later, the videotape w analyzed and vehicles in each lane were correlated with data as records downloaded from the trailer. The recorded data were documented in a Microsoft Excel spreadsheet with the time a vehicle passed the trailer to the nearest second and vehicle type. The downloaded text file from the trailer was imported into Microsoft Excel, and the videotaped data was entered into a separate worksheet in the same Excel file. Videotaped data records were matched against the radar trailer data, and misses (a vehicle 23 observed on video but not detected by the trailer) and phantoms (a vehicle detected by the trailer but not observed on video) were identified. The microwave radar trailer system may sometimes miss vehicles, particularly a small car obscured by a large truck in an intervening lane, and it may sometimes register phantom vehicles from extraneous radar echoes, e.g. from a truck in an adjacent lane. These phantoms and misses are tabulated for the trailer at location 5 in Table 1. The net error is also tabulated. This is the number of misses minus the number of phantoms, thus a positive value represents an undercount by the system (more misses than phantoms). Using the net error values multiplication factors were determined for adjusting the hourly vehicle counts. In Appendix A, the last columns of the tables show the adjusted number of vehicles per hour, which is the product of the hourly vehicle counts and the multiplication factors given in Table 1 for each lane. 24 Table 1: Misses and Phantoms Observed on I-76 near Rootstown Construction Zone, Ohio (08/20/04 Friday – 10:52AM-11:32AM) %?=MissesPhantoms Overall (N=767) 16 26 0.02086 0.0339 2.09% 3.39% Phantoms Misses Driving Lane (N=456) 8 9 0.01754 0.01974 1.75% 1.97% Phantoms Misses Passing Lane (N=321) 8 17 0.0249 0.0530 2.49% 5.30% Phantoms Misses Multiplication Factor 1.30% 1.0130 %?=MissesPhantoms Multiplication Factor 0.22% 1.0022 %?=MissesPhantoms Multiplication Factor 2.80% 1.0280 The trailer is also designed to measure the length of passing vehicles and to classify them into length bins. The system has been set up to use three length bins – class 0 is 0-20 feet, class 1 is 21-40 feet, and class 2 is 41 feet and above. Lengths of the vehicles were not measured per each vehicle, but from the videotaped the vehicles were grouped into large trucks (semis, all expected to be over 40 feet) and everything else or “cars”, with some identified as motorcycles. A comparison of the videotaped length categories to the trailer length and classification values from the trailer for August 20 is given in Table 2. 25 Table 2: Length Classification of Vehicles by Trailer Compared to Video Record for August 20, 2004 OU Vehicle Record OU Vehicle Record OU Vehicle Record car truck total percent clearly correct percent clearly incorrect car truck total percent clearly correct percent clearly incorrect car truck total percent clearly correct percent clearly incorrect Driving Lane Wavetronix Vehicle Class percent 21total correct <=20ft 40ft >40ft 263 2 265 99.25% 40 133 173 76.88% 303 135 438 86.80% percent incorrect 0.75% 23.12% 98.52% 90.41% 13.20% 1.48% 9.59% Passing Lane Wavetronix Vehicle Class percent 2140ft total correct <=20ft >40ft 261 1 262 99.62% 17 8 25 32.00% 278 9 287 93.88% percent incorrect 0.38% 68.00% 88.89% 93.73% 6.12% 11.11% 6.27% Both Lanes Wavetronix Vehicle Class 21percent <=20ft 40ft >40ft total correct 524 3 527 99.43% 57 141 198 71.21% 581 144 725 90.19% 9.81% 97.92% 91.72% 2.08% 8.28% percent incorrect 0.57% 28.79% 26 Converting Hourly Traffic Counts to Cumulative Inter-arrival Time Distributions IAT data were generated from the location 5 trailer at I-76 Westbound construction work zone near Rootstown with two lanes of traffic. Three days of traffic data were taken for the analysis and there was uninterrupted traffic flow at the trailer location. The average speed for driving lane was 65.3 mph and that for passing lane was 70.4 mph. The average speeds for each 15 minute interval during daytime for driving and passing lane are given in Appendix A. The speeds given in the tables were collected by the microwave radar trailers. The system records the moving average speed for the last 16 vehicles in the output. The average of two sensors moving average speeds were used in this study. Vehicles were recorded in the data file with a time stamp with a precision of 0.025 second. At every fifteen minutes, a line listing the number of vehicles observed in that period was inserted in the data file. There were 162 periods for the data collection...
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This document was uploaded on 02/26/2014 for the course E 515 at University of Louisiana at Lafayette.

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