Something that would help out with emissions? Less people driving. Easier said than done though. People have places to be, things to do. To help them choose other transportation options, one suggestion is congestion pricing, a fee for driving in congested areas.
This is obviously something that would be geared towards urban environments where public transportation is more plentiful and provides access to a wide variety of places. It’s sort of like a toll for driving in an area that has a lot of traffic instead of choosing the subway or bus for instance. London and New York City have already implemented this for certain areas and more cities may follow.
The fees generally go towards infrastructure for public transportation so the alternative system of travel is up kept. It helps cut down emissions by nudging people to drive less and when they are driving, they’re not sitting in traffic for so long. But who wants to pay extra? The subway and bus system is your friend.