Los Angeles is talking about a tax for drivers based on mileage. I guess you could document the odometer reading once a year, like during your smog check. Totals would include travel outside of the city. Another, maybe more fair measure, would be to track driving just in the LA area. Pay As You Drive (PAYD), or Usage-based insurance (UBI) is insurance based on factors including time and distance. The same solution might be an option for drivers in LA to report local driving distances. Maybe if they change habits like drive outside of busy rush hours they can reduce their tax. BSafeMobile can do all of the above.

https://en.wikipedia.org/wiki/Usage-based_insurance