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385 miles 39421 miles 1109 miles 76758 miles 1506

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Unformatted text preview: .07898 miles (4.0211 miles) 0.7424 miles (4.7635 miles) 2.131 miles (2.5571 miles) 0.0142 miles (0.4261 miles) 0.4119 miles (0.4119 miles) Figure 2: Trailer Locations Used in the I-76 Westbound Construction Zone Data Collection In the example, the trailer data collected from the fifth location was used. This location was about 1.5 miles before the start of the lane closure taper, which was reflecting the free flow characteristics of the traffic. The trailer data from location 5 was used for generating the cumulative probability distributions for the inter-arrival times, identifying the percentages of the vehicle types, and assigning the initial speeds for the vehicles. The trailer at location 6 was used for adjusting the speeds of the vehicles in the work zone. The data collected by the microwave radar trailers include time to the nearest millisecond, lane of traffic, and a set of data from the first sensor: a timestamp in 2.5-ms time increments, duration of the radar image in 2.477-ms time increments, a moving average speed based on the last 16 vehicles in mph, and a vehicle class [22]. Next the 19 same set of data for the second sensor, then an average of the two running average speeds in mph, vehicle length in feet, and per vehicle speeds for each sensor in mph. All speeds are rounded to whole mph values, and all lengths to even feet values. The trailer measurements were validated by measuring traffic separately for approximately half an hour at each trailer location, as shown in Figure 3. The traffic was videotaped with a time-stamped video. Later the videotape was analyzed and vehicles in each lane were correlated with data records downloaded from the trailer. Driving Lane (2) Passing Lane (1) Wavetronix Radar units on trailer ORITE Video Monitoring Lanes 1 & 2 West Bound Figure 3: Configuration of radar trailer and ORITE equipment for measuring traffic used in evaluation (adapted from Zwahlen et al. [22]) 20 3.1.3 Data Analysis The first step of the data analysis was separating daytime and nighttime traffic count data for the work zone in order to ident ify the difference in traffic volume during daytime and nighttime. Time from sunrise until sundown was assumed as daytime. The work zone data was collected between the dates 08/20/2004 and 08/22/2004 and the daytime was identified as the times between 6:45 AM to 8:15 PM. Three days of data were used in the study. The summary of the three days of data for driving lane and passing lane for nighttime and daytime durations are given in Appendix A. Data collected by the trailer was divided into 15 minute time intervals and analysis was performed with the 15 minute interval data sets. For each 15 minute interval, vehicle counts, average speeds, and average inter-arrival times were computed. Microwave radar sensor equipped trailers provide an exact time stamp when a vehicle passes by the trailer. The difference between two consecutive time stamps gives the inter-arrival time for those two vehicles. After the counts were calculated for 15 minutes, each of the 15 minute counts were multiplied by 4 in order to get the hourly vehicle counts. The analysis of daytime and nighttime IAT distributions showed that there was not much difference in the IAT distributions between day and night. For similar hourly traffic counts, almost the same average inter-arrival times were observed for daytime and nighttime traffic data. In Figure 4, the traffic volume versus average inter-arrival time comparison for daytime and nighttime are both given for driving lane for 3 days of data. Figure 5 shows the comparison for passing lane. The difference in the hourly traffic counts can be easily observed in the figures as it was expected. The figure also shows that 21 the average inter-arrival time for a given time interval is dependent on the number of vehicles per time interval. Average inter-arrival time for daytime driving lane traffic was 6.28 seconds with a standard deviation of 2.31 seconds. Average inter-arrival time for nighttime driving lane was 17.98 seconds with a standard deviation of 9.94 seconds. Daytime-Driving Lane N=162 Average=6.28 sec Standard Deviation=2.29 sec Minimum=4.61 sec Maximum=20.90 sec Number of Vehicles per Hour 100 Nighttime-Driving Lane N=126 Average=17.98 sec Standard Deviation=9.94 sec Minimum=5.26 sec Maximum=52.53 sec 10 1 0 100 200 300 400 500 600 700 800 900 Average Interarrival Time (sec) Daytime-Driving Lane Nighttime-Driving Lane Figure 4: Comparison of Average Inter-arrival Times versus Number of Vehicles per Hour for Daytime and Nighttime Driving Lane Data Average inter-arrival time for daytime passing lane traffic was 12.07 seconds with a standard deviation of 8.70 seconds. Average inter-arrival time for nighttime passing lane was 135.04 seconds with a standard deviation of 229.16 seconds. The difference in the average inter-arrival times was due to low traffic counts during nighttime. 22 Daytime-Passing Lane N=162 Average=13.99 sec Standard Deviation=17.12 sec Minimum=5.62 sec Maximum=152.50 sec Number of Vehicles per Hour...
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