A high number of street dealers operate in the open-air drug market in the Red Light District in Amsterdam, The Netherlands selling cocaine and ecstasy to visitors. This is a nuisance to shop owners and inhabitants in the area. To mitigate this problem, the Municipality of Amsterdam installed three text-based light projections on the pavement and walls of a specific street known for attracting high numbers of dealers. The text discouraged visitors from buying drugs from street dealers. The aim of the intervention was to displace dealers from the specific street to surrounding areas. In order to investigate the influence of this intervention, we collected and analyzed video footage from two CCTV cameras located in the street. We analyzed a total of 765 one-minute segments of video footage from before and after the intervention was implemented. The analysis of the video footage showed that there were statistically significantly fewer street dealers observed in the street after the intervention was implemented. This difference amounted to an approximately 25 percent reduction of observed street dealers, when we controlled for time of day, day of the week, and the crowding of the area. These results indicate that the light-based interventions successfully discouraged street dealers from operating in the street. This influence of the intervention might be connected to the nature of the Open-Air Drug market in the Red Light District, which is almost exclusively catering to tourists and where dealers are constantly moving around rather than standing still. The generalizability of the current study to other open-air drug markets therefore remains uncertain.