Objective Behavioural interventions, such as smoke-free signage, are used to support air quality in public outdoor spaces that are not protected by a smoke-free policy, such as states with preemptive clause legislation. However, there is little evidence of the effectiveness of these interventions. This paper is an evaluation of whether smoke-free signage posted in public parks altered smoking behaviours of park patrons.

Methods A time-series quasi-experimental design was used. Cigarette butts were collected at the same day and time every week in ten amenities within four parks in 2011. Each park completed a baseline period until a stable trend emerged at six weeks, then received smoke-free signage for the six week intervention period. There were 1684 cigarette butts collected during baseline and 1008 collected during the intervention phase.

Findings Wilcoxon signed-rank test demonstrated that smoking at seven out of ten amenities decreased and the overall decrease was significant at p=0.028. Individual parks and amenities grouped by type did not experience a statistically significant change. A neighbourhood median income trend was visually discovered, revealing that as income increased, there was a greater decrease in cigarette butts.

Conclusions This study provides evidence on the impact of smoke-free signage not supported by local ordinance in public parks using a reproducible measure. States, especially those with a preemptive clause legislation, may benefit from incorporating smoke-free signage in public areas to protect community members from exposure to tobacco smoke, reduce littering, and denormalise smoking.