Sexual violence is a major threat to women living in the urban slums of India, where structural limitations often render traditional interventions ineffective. This study evaluated the effectiveness of a low-cost community-based alarm intervention in preventing sexual victimization in informal urban settlements. A single-blind cluster randomized controlled trial was conducted across 20 blocks of slums in Delhi. Five hundred adult women were randomized by block into the intervention (nine blocks; n = 239) and control (11 blocks; n = 261) groups. The intervention included the distribution of personal safety alarms and community-based training workshops. Data on sexual victimization and interpersonal trust were collected before and after the 6-month intervention. Of the 500 participants, 485 (intervention group, n = 226; control group, n = 259) completed both assessments. The rates of lifetime sexual victimization were high at baseline: stalking ( n = 413, 84.9%), verbal harassment ( n = 338, 69.7%), and non-consensual physical contact ( n = 304, 62.7%). Significant group-by-time interaction effects were observed for reductions in underwear theft (odds ratio OR = 0.207, 95% CI 0.062, 0.694) and non-consensual physical contact ( OR = 0.199 0.059, 0.670). Other types of victimization declined over time in both groups. A significant main effect of time on interpersonal trust was also observed ( F 1, 966 = 40.47, partial η 2 = .040, p < .001). This context-sensitive intervention effectively reduced opportunistic sexual violence and improved interpersonal trust among participants. The community self-defense method offers a pragmatic and scalable harm reduction approach for high-risk settings in the absence of a formal protection infrastructure. Trial registration: Trial registry name, URL, and registration number: UMIN-CTR ( https://www.umin.ac.jp/ctr/index-j.htm ), ID# JPRN-UMIN000050136.
Harada et al. (2026) studied this question.