A post-implementation survey was administered to the agencies that participated in the implementation study. The survey sought to identify issues that had to be dealt with to implement the flashing yellow arrow display, the cost to the agency to implement the flashing yellow arrow display, and whether there was support within the agency and outside the agency for the flashing yellow arrow display.
Overall, each of the participating volunteer agencies experienced favorable results with the flashing yellow arrow display implementation. The most commonly reported problem was overcoming the current design of controllers and conflict monitors. In all cases, the participating agencies had to use either internal logic (e.g., command box in the Wapiti firmware for the Type 170 controller) or some type of external logic or relay device to implement the flashing yellow arrow display. These changes were necessary because the permissive flashing yellow arrow and circular green through movement indications could not illuminate simultaneously (prior to conversion, the circular green indication was used to communicate both the through and permissive movements).
It is assumed that new controller software and any significant upgrade of existing controller software will include this functionality so that, over time, external logic will no longer be needed. The special logic described above can be implemented using a “logic box” external to the signal controller, or with software enhancements in the signal controller.
The cost to implement the flashing yellow arrow display was relatively low (approximately $750 for new signal heads and about 200 man-hours total). All agencies received significantly more positive than negative comment from the public and from their own staff.
In addition to the formal written survey response comments, there was a fair amount of anecdotal evidence that provided preliminary insight into the agencies’ perspective on use of the flashing yellow arrow display. The overall response to the flashing yellow arrow display from traffic engineers around the county was positive. In general, traffic engineers expressed their approval of the flashing yellow arrow display because:
In general, local law enforcement agencies were supportive of the flashing yellow arrow display however, there was some hesitation from city councils or county commissioners. Their concern was largely focused on the issue of trying something new that was not formally part of the MUTCD.
Public comments from citizens who experienced the flashing yellow arrow display in the field were generally positive. Several volunteer agencies reported receiving e-mails or written letters from the motoring public with most, if not all, in support of the flashing yellow arrow display.
As part of the on-going study activities, the Research Team observed driver reaction to the flashing yellow arrow display immediately upon implementation in the field. The drivers’ responses to the new displays suggest there was very little confusion, with most drivers driving through the intersection as if nothing were changed. Interestingly, at least one agency that has implemented the flashing yellow arrow display reported that drivers waiting to make a permissive left turn now stop behind the stop bar and wait for a gap in opposing traffic (as opposed to entering the intersection before stopping).