Adopt-a-Highway volunteers will be joining participants across the country for National CleanUp Day this Saturday, with local volunteers serving in 13 of Arizona’s counties. ADOT officials say volunteers from all 50-states will focus on cleaning green spaces, urban landscapes and waterways. Overhead message boards will be up to remind motorists to be on the lookout for volunteers working alongside the highway picking up litter. Drivers are encouraged to slow down and move over when possible. Drivers should also watch for volunteers on local streets.