This is an aggressive setup that attempts to squeeze out every last ounce of capacity. But it adds very little increased capacity for leading left setups and creates a perceived yellow trap in lagging left setups (and perception is reality.. if a driver believes their left turn phase is ending it’s just as dangerous as an actual yellow trap). It’s confusing to see the left turn arrow flashing yellow when the adjacent through is still red and many agencies refuse to operate the FYA in this manner. In addition, many agencies favor leading left operation to prevent the perceived yellow trap situation altogether. If they do run lagging lefts, they tie the left turns together to ensure that they start and end simultaneously.
Total bollocks. There are FYAs in nearly all jurisdictions within 400 miles of me , yet not a single one (
AFAIK) operates FYAs in this manner, probably because it doesn't make any sense. Some do have odd quirks:
- protected-only based on time of day (although increasingly normal)
- longer all-red phases between the protected and permissive phase (though some have none, such as many left turns in Seattle)
- red while pedestrian has walk sign
...but none have any sort of through/left synchronization. That completely ruins the whole point of the FYA. I understand the perception, but I think in reality, this has more to do with poor signal placement, where drivers can only see the left turn signal in their upper peripheral vision. Federal Way, WA (an agency near me that I have brought up
just about a thousand times before) uses lead/lag or lagging at almost every intersection. They also go protected-only during parts of the day. Needless to say, they are using the FYA to the fullest extent possible. Yet not a single shred of data that I've ever read, in regards to FYA performance in the city, suggests in increase due to perceived yellow trap. There's not a lot of publicly available data, but one the PDFs from several years ago suggests that FYAs seem to work better when there's secondary/auxiliary signals (
PDF page 14). Also, that safety performance improves dramatically after the first year.