Jackson County, OR

Jackson County, Oregon, pursued a somewhat unique path with its implementation of the flashing yellow arrow display. The county traffic engineer for Jackson County approached the Research Team to implement the flashing yellow arrow display in the county. The County had only one intersection that could be converted over from existing PPLT to the flashing yellow arrow display that met the research project’s requirements. The County submitted the FHWA request for experimentation and it was approved by FHWA. The single intersection began operating with a flashing yellow arrow display using a four-section all-arrow vertical display face.

Since initial implementation in 2001, Jackson County converted five existing exclusive (protected only) left-turn operations to PPLT control with a flashing yellow arrow display. However, in these installations, the County used a three-section vertical display face – the center indication was used for the yellow arrow clearance (following the circular green indication) and the flashing yellow arrow (permissive period) indication. The County pursued this approach to eliminate the cost of a new display face (four-section) and running additional wire cable and to address vertical clearance issues.

The County submitted a request to FHWA for approval to implement the 3-section arrangement of the flashing yellow arrow display. The request was originally denied by FHWA but later recanted by FHWA after reviewing a video clip of the intersection showing the operation. The video clip showed the adjacent thru signals going to yellow at the same time as the flashing yellow arrow changed to a steady yellow arrow in the same section. The ability of left-turn drivers to see the thru signals going yellow made it less necessary for the change from the flashing yellow arrow to the steady yellow arrow to be positional. Accordingly, FHWA issued a letter authorizing the County to implement the 3-section PPLT flashing yellow arrow display. Figure 1 below illustrates Jackson County’s retrofit of a three-section display and the corresponding operation of the signal.

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