In April 2023, the California Air Resources Board (CARB) passed its Advanced Clean Fleets (ACF) rule, which will require California medium- and heavy-duty truck and bus fleet owners with over $50 million in annual revenue to transition to zero emission vehicles through a phaseout of their existing internal combustion engine–powered vehicles by 2045. On July 26, 2023, while the ACF rule was pending with the California Office of Administrative Law for a final determination prior to release, CARB withdrew the regulatory package with the intention of resubmitting it “at a subsequent date.” CARB is now forming a Truck Regulation Advisory Committee and, on August 22, 2023, will host a public meeting to discuss and solicit feedback on future efforts to implement the ACF rule. Instructions for participation in this public meeting can be found here.