“It’s illegal to buy drugs from street dealers” a video-based pre-post study of a behavioral intervention to displace dealers from an Amsterdam open-air drug market

Objectives  A high number of street dealers operate in the Red Light District in Amsterdam, The Netherlands. To displace the dealers, the Municipality of Amsterdam installed text-based light projections in a street attracting a high number of dealers.
Methods  To evaluate the intervention, we did a pre-post analysis of video footage from two CCTV cameras located in the street. In total, we analyzed 765 one-minute segments of footage from before and after the implementation.
Results  The implementation was followed by a four percentage point reduction in street dealers. However, the estimated effect shows fragileness with wide confidence intervals and a p-value just below 0.05, and a Bayesian robustness analysis suggests that the intervention was not associated with the outcome.
Conclusions  Analyzing CCTV-footage offers a unique avenue for evaluating small scale interventions in open-air drug markets. While we observed a decrease in the presence of dealers, the intervention still needs further validation.