Multiple incentives in encouraging car pool formation on a university campus.

Tanguay et al. (1982) tried to get more college students to car pool. They handed out 25-cent coupons and set aside special parking spots for cars with two or more riders.

The team watched campus lots for two months. They counted cars with only one student and cars with two or more.

Car pooling went up in the lots that got coupons and reserved spots. It stayed the same in lots that got nothing.

When the coupons stopped, the new car-pool habit did not drop back. The reserved spots seemed to keep the change alive.

Berler et al. (1982) and Haring et al. (1988) saw the opposite. When they pulled away raffle tickets or free soft drinks, seat-belt use fell right back. The difference: E et al. kept the reserved parking while the others removed every reward.

Reed (1991) got bigger gains by adding police checks to the token plan. That mix pushed seat-belt use up almost forty percent among young drivers, well above the small jump E et al. saw for car pooling.

Glenn (1983) showed the same small, cheap token can work for two safety acts: seat belts at one factory and car pooling on one campus. The lesson: size of reward matters less than making it easy to get.

You can run this on any campus or worksite tomorrow. Pick a low-cost perk like prime parking. Pair it with a tiny daily reward. Keep the parking; drop the coins. The spot alone may hold the new habit in place.