It is always worth noting environmental regulations that aren't being pioneered in California:
The Idaho Department of Environmental Quality wants drivers to turn their cars off rather than let them idle.[...]
Nampa Mayor Tom Dale said Monday he hasn't yet heard from the DEQ, but that he thinks it would be good to encourage people to turn their cars off if they have a chance.[...]
According to the U.S. Environmental Protection Agency, it is more gas-efficient to turn the engine off and restart the vehicle if idling is expected to last more than 30 seconds.
A number of New England states and Canadian provinces have no-idling zones for personal vehicles in urban areas. To implement this sort of policy in California, however, would mean telling millions of Californians stuck in traffic on a daily basis to shut off their enginesâ€“permanently.