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OCR for page 58
58
100%
11.4% 12.6%
90%
34.1%
80% Proceeding
51.8% through
70%
Crosswalk
60%
50%
88.6% 87.4%
40%
65.9%
30%
Stopped or
48.2%
20% Stopping
10%
0%
Flash Yellow Solid Yellow Solid Red Flash Red
Signal Phase
This figure shows a bar chart of driver behavior in regard to the four PHB signal displays: "Flashing Yellow/Don't Walk,"
"Yellow/Don't Walk," "Red/Walk," and "Flashing Red/Flashing Don't Walk." The results are discussed in the text.
Figure 22. Evaluation of driver behavior at PHB.
vehicular delay by allowing drivers to proceed during the 6-week driver adaptation period prior to the posttest. Further,
"Flashing Red" phase. The following analysis is intended to frequent tourist and non-commuter traffic in the area may
capture driver understanding of and compliance with the sig- have contributed to driver confusion. Given the apparent lack
nal indication. of understanding of the PHB, it seems that the flashing red
Driver understanding of and compliance with the PHB can indication of the traffic control was not intuitive to drivers.
be evaluated by relating the driver stopping behavior to the
indicated signal phase. Figure 22 plots two categories of driver Impact on Vehicular Traffic
behavior for each signal phase: (1) vehicles stopped or stop-
ping, and (2) vehicles proceeding through the crosswalk. The Raised Crosswalk
figure shows four signal phases that correspond to the PHB A pretest and posttest speed study was performed at the
phasing sequence for vehicles: "Flashing Yellow," "Solid Yel- RCW installation to estimate the impact of the treatment
low," "Solid Red," and "Flashing Red." installation on free-flow vehicle speeds. All speeds were col-
The figure shows that 34.1% of drivers proceeded through lected from video observations using known reference dis-
the crosswalk in "Flashing Yellow," which is permitted behav- tances from roadside markers. The speeds correspond to the
ior. As the signal changed to "Solid Yellow," 11.4% of drivers average speed just upstream of the crosswalk, measured over
proceeded through the crosswalk, which is allowable if the a distance of approximately 100 ft at exit and 160 ft at the entry
vehicles were too close to the crosswalk to come to a stop. How- leg. The study included only free-flowing vehicles that passed
ever, even during the "Solid Red," 12.6% of observed vehicles through the crosswalk in the absence of pedestrians. A sample
proceeded through the crosswalk. This statistic is a concern, size of approximately 100 vehicles was collected for the entry
since drivers are legally required to stop for the red signal indi- and exit leg of the roundabout in both pretest and posttest
cation and because pedestrians expect a crossing opportunity. conditions. The total dataset of 405 observations was collected
Driver behavior during "Flashing Red" shows that almost for different times of day and on different days of the week.
half of the drivers (48.2%) remained stopped, suggesting some The results show an average entering speed approaching
inefficiency in driver behavior in response to the PHB. the crosswalk of 25.3 mph, which was significantly reduced
These findings raise some concerns that the PHB traffic to 20.5 mph with the installation of the raised crosswalk
control device may not have been properly understood by (p < 0.0001). While this speed reduction is as anticipated,
drivers or that the PHB display was ignored. An education the posttest speeds were still relatively high given the RCW
campaign by the city of Golden, using web and news media treatment. This is attributed to the relatively low vertical
outlets, informed citizens of the PHB installation at the test height and gentle slope transition that was used in the RCW
roundabout and discussed appropriate behavior. However, it design. The design therefore results in a relatively low impact
is unclear how frequently the device was actually used in the on vehicle speeds in the absence of pedestrian and vehicle
