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From page 22... ... 22 Objective Prior to development of guidelines for timing the yellow change and red clearance intervals, it was first necessary to understand the behavioral characteristics of drivers approaching an intersection during the yellow and red intervals. Although relevant behavioral characteristics have been evaluated in past research, there are limitations to the current body of knowledge. Read the entire page →
From page 23... ... 23 – 72 to 96 feet. – 96 to 120 feet. Read the entire page →
From page 24... ... 24 major theme parks and sports stadiums in greater Orlando and southern California with the intent of having a larger sample of drivers unfamiliar with the sites. Field Data Collection Procedures Behavioral data were collected at the 83 signalized intersection approaches between October 2009 and July 2010. Read the entire page →
From page 25... ... 25 that was connected to the camera using a long RCA patch cable. Minor adjustments to the field of view, such as turning the pole/camera left or right, could be made while observing the viewing screen of the monitor. Read the entire page →
From page 26... ... 26 the cameras allowed for observation of all characteristics relevant to the behavioral evaluation, including the traffic signal indications, brake light indications, location of the vehicle with respect to the stop line, vehicle type, spacing between successive vehicles, whether the vehicle stopped or went through, and whether red-light running occurred. A general schematic of a typical video camera installation is shown in Figure 4. Read the entire page →
From page 27... ... 27 • Time of day; and • Vehicle type. Vehicles were excluded for any of the following reasons: • Was not a first-to-stop or last-to-go vehicle within the respective lane, • Turned right or left or u-turn at the intersection, • Began braking prior to the onset of yellow (stopping vehicles only) Read the entire page →
From page 28... ... 28 The travel time to the stop line at the onset of yellow was estimated by dividing the subject vehicle's distance from the stop line at the onset of yellow by its approach speed. Note that this provided only a prediction of the travel time based on the approach speed and distance upstream and was not the actual travel time, which may vary due to acceleration or deceleration. Read the entire page →
From page 29... ... 29 to the intersection at the start of yellow. Two forms of the logistic regression model were formed: one based solely on travel time and another including both travel time and speed. Read the entire page →
From page 30... ... 0 10 20 30 40 50 60 70 80 90 100 2.0 2.5 3.0 3.5 4.0 4.5 5.0 5.5 6.0 Travel Time to Stop Line at Start of Yellow (s) Pe rc en t o f V eh ic le s Went-Through Stopped Figure 7. Read the entire page →
From page 31... ... 31 in the figures, for comparative purposes, are the distributions of data reported in select previous studies. The basic descriptive statistics for brake-response time and deceleration rate are shown in Table 12. Read the entire page →
From page 32... ... 32 – increased as travel time to the intersection at the start of yellow increased (i.e., drivers reacted more slowly when farther from the intersection) ; – increased as the deceleration rate increased (i.e., drivers decelerating more rapidly used longer brake-response times) Read the entire page →
From page 33... ... Highly Significant Factors Significant Factors Insignificant Factors Brake-Response Time • Travel Time to Stop Line at Start of Yellow • Approach Speed • Deceleration Rate • Approach Grade* • Speed Lim it • Vehicle Type • Peak vs. Read the entire page →
From page 34... ... 34 Travel Time to Stop Line at Start of Yellow Brake-Response Time (s) Deceleration Rate (ft/s 2 ) Read the entire page →
From page 35... ... 35 Speed Limit Range Deceleration Rate (ft/s 2 ) 25 m ph to 30 m ph Num ber of Vehicles 267 Mean 8 .21 Standard Deviation 2.24 Percentiles 15 6 .17 50 7 .85 85 1 0.67 35 m ph to 40 m ph Num ber of Vehicles 540 Mean 9 .79 Standard Deviation 2.80 Percentiles 15 7 .32 50 9 .21 85 1 2.31 45 m ph to 50 m ph Nu mb er of Vehicles 1444 Mean 10.29 Standard Deviation 2.78 Percentiles 15 7 .63 50 9 .83 85 1 3.10 55 m ph to 60 m ph Num ber of Vehicles 207 Mean 11.80 Standard Deviation 2.53 Percentiles 15 9 .50 50 1 1.42 85 1 4.18 Table 16. Read the entire page →
From page 36... ... 36 0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0 11.0 12.0 13.0 14.0 15.0 25 to 30 mph 35 to 40 mph 45 to 50 mph 55 to 60 mph Speed Limit Range D ec el er at io n Ra te (f t/s 2 ) 85th Percentile Mean 15th Percentile Figure 13. Read the entire page →
From page 37... ... 37 0.0 1.0 2.0 3.0 4.0 5.0 6.0 7.0 8.0 9.0 10.0 11.0 12.0 13.0 14.0 15.0 ≤ 4.0 s 4.1 - 4.9 s ≥ 5.0 s Yellow Duration Range D ec el er at io n Ra te (f t/s 2 ) 85th Percentile Mean 15th Percentile Figure 14. Read the entire page →
From page 38... ... 38 and left-turning vehicle speeds with respect to the posted speed limit. The primary outcome was to develop a rule-ofthumb approach speed recommendation for use in the calculation of yellow change and red clearance intervals in lieu of 85th percentile speed data. Read the entire page →
From page 39... ... 39 y = 0.8846x + 11.369 R2 = 0.8271 30 35 40 45 50 55 60 65 70 20 25 30 35 40 45 50 55 60 Speed Limit (mph) Read the entire page →
From page 40... ... 40 average, 0.39 mph greater than the speed limit, while the 85th percentile speeds were, on average, 6.49 mph greater than the speed limit. The results indicate that for practical purposes, the speed limit provides a good estimate of the mean speed of freeflowing vehicles approaching a signalized intersection. Read the entire page →
From page 41... ... 41 vehicles were 10.59 mph less than the posted speed limit. The overall 85th percentile left-turn approach speeds were 4.94 mph less than the posted speed limit. Read the entire page →
From page 42... ... 42 sample. An example of the intersection entry delay assessment is shown in Figure 18. Read the entire page →
From page 43... ... 43 Primary Approach Adjacent Approach State Red (s) Average Start-Up Delay After the Start of Green (s) Read the entire page →

From page 22...

... 22 Objective Prior to development of guidelines for timing the yellow change and red clearance intervals, it was first necessary to understand the behavioral characteristics of drivers approaching an intersection during the yellow and red intervals. Although relevant behavioral characteristics have been evaluated in past research, there are limitations to the current body of knowledge.