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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