UK oriented, here. Adjust penalty labour as appropriate to your country.
When identified, round 'em all up. Chain them together in stripy pj's. Give them litter sticks. Send them out to tidy up the roads. let them experience the inconvenience of putting their lives on the line (plenty of messages on uk motorways about how people are at risk to pick up litter), or generally having their lives disrupted.
10 days labour, irrespective of the weather for Offence 1. Escalate sentence as appropriate.
whippings optional