Page "Broken windows theory" Paragraph 13

Under the broken windows theory, an ordered and clean environment – one which is maintained – sends the signal that the area is monitored and that criminal behavior will not be tolerated.

Conversely, a disordered environment – one which is not maintained ( broken windows, graffiti, excessive litter ) – sends the signal that the area is not monitored and that one can engage in criminal behavior with little risk of detection.