Description | The percentage of illegal parking in spaces reserved for the physically disabled was monitored under three sign conditions: ground markings, ground markings plus vertical signs, and vertical signs containing a message that concerned citizens were watching the spaces. Illegal parking dropped from 69.3% of 102 vehides during the initial ground-sign condition to 57.3% of 36 vehides in the first vertical-sign condition. Following removal of the vertical signs, illegal parking increased to 68.7% of 43 vehides. During the second vertical-sign condition, illegal parking dropped to 53.7% of 32 vehides, followed by an increase to 69.5% of 68 vehides after the vertical signs were removed. The lowest rate of illegal parking (27.1% of 78 vehides) occurred in the vertical-sign-plus-message condition. Illegal parking subsequently increased to 34.6% (of 94 vehides) when the message sign was removed, followed by an increase to 65.2% (of 105 vehides) when the vertical signs were removed. Originally published Journal of Applied Behavior Analysis, Vol. 24, No. 1, Spring 1991 | en_US |