How can photochemical smog be controlled?

Catalytic converters force $CO$ and incompletely combusted hydrocarbons to react with a metal catalyst, typically platinum, to produce ${CO}_{2}$and ${H}_{2}O$. Additionally, catalytic converters reduce nitrogen oxides from exhaust gases into ${O}_{2}$ and ${N}_{2}$, eliminating the cycle of ozone formation.