The complaint cuts across modes. Cyclists say unsolicited waves from drivers undermine the predictability that keeps intersections safe. When one driver defers out of turn, other vehicles moving through the same intersection have no way of knowing the rules just changed. The cyclist, now in motion on someone else's cue, is exposed to traffic that hasn't gotten the memo.

The pattern has a name among safety advocates: the "wave of death," a scenario in which a driver gestures a pedestrian or cyclist forward while a second vehicle, unaware of the informal yield, proceeds normally. The result is a collision the informal gesture directly enabled.

Commenters across Bay Area discussion forums — cyclists and drivers both — landed on the same formulation: be predictable, not nice. The argument is not that courtesy is bad, but that improvised deference at intersections introduces ambiguity that right-of-way rules are specifically designed to eliminate.

None of this is codified in any pending ordinance or SFMTA proposal. But the conversation reflects a live tension in how the city's mixed-mode streets actually function versus how traffic law assumes they will.

SFMTA's 2024 Vision Zero action plan includes intersection safety as a priority, with focus on high-injury corridors. Whether informal driver behavior — as opposed to signal timing, signage, or enforcement — falls within that scope has not been addressed publicly by the agency.

The next Vision Zero Steering Committee meeting has not been publicly scheduled as of this writing. SFMTA's quarterly safety report is due for presentation to the SFMTA Board in the coming weeks.