Ninety per cent of Danes care about littering, but one in three occasionally leaves rubbish in parks or street. Students from Roskilde University sought to use nudges to plug this gap. Sweets were handed out to members of the public and the students counted the sweet wrappers they found on the street. The experiment was repeated but the second time green footprints were placed on the ground leading to bins. The result was an almost fifty percent reduction in the number of sweet wrappers found on the street.