I am always looking for mechanisms that evince the body politic at work.

For the record, drivers have a group behavior that suggests a common understanding.

On the Golden Gate Bridge there are signs that say: “Double fine for exceeding 45 mph”. This worked. Drivers on the GG bridge go 45 mph.

About six months after this sign was put up on the Golden Gate, the Bay Bridge put up the same sign with the limit at 50 mph.

Drivers did not respond to the new threat of punishment on the Bay Bridge.

My conclusion. Drivers could see that the two-way traffic on the Golden Gate posed a safety hazard and that the 45 mph limit was a reasonable solution to head-on crashes.

The Bay Bridge is one-way on each level. There is no potential for head-on crashes and drivers see no safety reason for obeying the law or responding to the feeble threat.

The body politic is always pretty smart.