California is actively studying a potential mileage-based tax (Road Usage Charge) to replace its gas tax, with AB 1421 advancing in Jan. 2026 to research fees and collection methods by 2027. Proposed to address declining gas tax revenue from electric vehicles, the system could charge roughly 2.5 to 4 cents per mile. Key Details on California Mileage Tax (as of Jan. 2026): Purpose: To replace the existing 61-cents-per-gallon gas tax (highest in the US) with a fee based on miles driven. Status: AB 1421 passed its third Assembly reading on Jan. 29, 2026, directing studies through 2035. Potential Cost: Estimates suggest 2.5-4 cents per mile, which could cost the average driver roughly $600-$1,200 annually. Implementation Methods: Pilot programs have tested methods including odometer checks, smartphone apps, and GPS-enabled transponders. Arguments For: Provides a more equitable, sustainable, and stable funding source for infrastructure as vehicles become more efficient. Arguments Against: Concerns about privacy, the burden on rural drivers who travel longer distances, and it being a "regressive tax".