Intervening public spaces by subtraction: a randomised controlled trial in Montevideo, Uruguay

Perceptions of quality and safety are key determinants of people's use of green public spaces. Waste mismanagement, and particularly littering, are among users' main concerns. This research helps fill three gaps in the literature. First, we introduce a counter-intuitive approach of intervening public spaces by subtraction instead of addition (i.e. removal of street furniture). Second, we conducted a randomised controlled trial with a structural intervention in a real-life field setting. Third, we provide an empirical study from the Global South (Uruguay) on a topic - littering - that has mostly been studied only in the Global North. We assess the effect of removing trash bins on the amount of waste in public squares and on citizens' perceptions regarding the infrastructure, greenspace, cleanliness, and overall condition of the squares. We found that the intervention reduced the amount of litter in the squares by an estimated 43.5 %, yet did not significantly affect people's perception of square cleanliness. Our research provides evidence of the impacts of these interventions, and also highlights the need to further explore the causal mechanisms behind perceptions of quality green public spaces.