Community intervention to deter illegal parking in spaces reserved for the physically disabled.

The team wanted to stop drivers from parking in spots for people with disabilities. They set up a clear sign and a box that handed out polite reminder notes. Drivers could take a note and place it on any car that was parked illegally.

The study ran in a busy store lot. It used an ABAB design: baseline, signs on, signs off, signs on again. Each phase lasted several days.

When the note box was in place, illegal parking dropped from about half of all cars to about one quarter. When the box was removed, violations crept back up. Putting the box back again cut the problem almost in half.

The result lines up with Capehart et al. (1980). They added a bright plywood "har" to trash cans at football games. Litter doubled, just like parking compliance here jumped with a cheap visual cue.

Fritz et al. (2017) also used an ABAB reversal to change adult behavior. They made trash disposal harder and saw recycling rise. Both studies show that small tweaks, not big rules, can steer community choices.

Barber et al. (1977) paid college students to drive less and cut mileage by 20%. G et al. got a similar-size drop in illegal parking with free reminder slips instead of cash prizes. The tools differ, but the pattern is the same: clear contingencies change driver habits.

You can copy this setup anywhere you manage a parking lot, school, or clinic. One sign, one box of notes, and willing bystanders cut violations fast. No tickets, no staff, no cost after setup. Try it Monday: place a friendly note dispenser by your reserved spaces and invite staff or clients to hand them out.