Design Guidance for Freeway Mainline Ramp Terminals (2012) / Chapter Skim
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Pages 103-114
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From page 103... ...
103 This portion of the research focused on investigating driver behaviors while performing merge and diverge maneuvers onto and off of freeways. There are a number of ways to explore behavioral tendencies and patterns, both directly and indirectly.
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From page 104... ...
104 the study to offer additional instructions as needed: one researcher sat in the front passenger seat, giving directions and acting as a safety observer, while the other researcher served as the data recorder, sitting in the rear passenger seat and operating the computer. Subjects were instructed to drive normally, obey the speed limit, and follow the driving directions offered during the course, but they were not told that freeway merging and diverging were the focus of the study.
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105 3. Point at which the ramp edgeline changes from white to yellow, and 4.
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106 Technicians also reviewed the video to classify three types of pedal activities related to foot movements, using the terms in Table 45. Using the locations of the key points on each ramp, researchers identified when each driver passed the beginning of the ramp, passed the change in edgeline, made the lane change to initiate the merge/diverge maneuver, and passed the end of the ramp.
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From page 107... ...
107 painted nose. It also shows the following driver and vehicle characteristics corresponding to those times and locations: • The stage of the ramp being traversed, expressed as a numerical code: – 5 = within 10 s before passing Point 1, – 10 = Stage 1, between Points 1 and 2, – 20 = Stage 2, between Points 2 and 3, – 30 = Stage 3, between Points 3 and 4, and – 40 = Stage 4, within 10 s after passing Point 4; • Throttle and brake pedal use; • The presence of a lead vehicle ahead of the instrumented vehicle near enough to affect the subject's desired speed; • The occurrence of any glances by the subject into a mirror or through the side window.
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From page 108... ...
108 the appropriateness of a gap identified previously. Based on the data summarized in the tables, a merging driver traveled 100 to 200 ft and increased speed by 2 to 3 mi/h during an average glance.
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From page 109... ...
109 -50% 0% 50% 100% 150% 200% 250% 300% 350% 1 3 5 7 9 11 13 15 17 % o f S CL Ramp Number Subject Data Average SC L le ng th (f t)
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From page 110... ...
110 resents the acceleration rate of one subject on an entrance ramp; the solid line connects the average rate for each ramp. The data table attached to the chart shows the summary statistics for each ramp.
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From page 111... ...
111 • No Pedal Time: The elapsed time between the deactivation of throttle and the activation of brake (i.e., the amount of time when neither throttle nor brake was in use)
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From page 112... ...
112 SCL for one subject on an exit ramp, and the solid line connects the average SCL distance values for each ramp. The data table attached to the chart shows summary statistics for each ramp.
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From page 113... ...
113 6.4.3 Deceleration Similar to the acceleration analysis for entrance ramps, researchers used the speed and time data from each subject to develop speed profiles for each subject on each exit ramp, which were then used to evaluate deceleration patterns. Figure 62 shows the recorded deceleration rates for each subject on each ramp, represented as constant deceleration from the diverge point (Point 2 in Figure 56b)
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From page 114... ...
114 deceleration values were less than assumed in the Green Book, none of the drivers appeared uncomfortable and likely could have tolerated greater deceleration if necessary. 6.5 Summary of Significant Findings The most significant findings from the examination of behavioral data are as follows: • In uncongested or lightly congested conditions, a typical glance into a mirror or over the shoulder by a driver merging onto the freeway is typically about 2.5 to 3.0 s, but the driver tends to take three such glances on a given entrance ramp.
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