Messages announcing the possibility of community intervention and the
time of its occurrence were used to examine illegal parking in spaces
reserved for the disabled, during specified and nonspecified time peri
ods. Observations were recorded during two consecutive 1-hour shifts (
4:00 to 5:00 p.m. and 5:00 to 6:00 p.m.). An ABACA reversal design was
used at Space 1 and an ABACAB reversal design was used for Spaces 2 a
nd 3. A sign was used to indicate that either the 5:00 to 6:00 p.m. (B
) or the 4:00 to 5:00 p.m. (C) shift was under observation. Although t
he results from Space 1 showed the same pattern as found in Spaces 2 a
nd 3, they were not statistically significant. These findings suggest
that illegal parking was probably controlled more by the content of th
e message than by the increased salience resulting from the addition o
f a secondary message sign.