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Field
Trial Status
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Before
completed
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After
on_going
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Field
Trial End Date
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Before
January 22, 2026
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After
September 30, 2026
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Field
Last Published
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Before
March 27, 2026 01:09 PM
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After
March 27, 2026 02:36 PM
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Field
Intervention (Public)
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Before
Safety in public spaces is a global concern that can negatively impact individuals’ well-being, cause them to avoid certain activities, and lead to additional expenditures to feel secure. In this study, we document the prevalence of safety concerns and experiences of harassment among university students in the UK. We evaluate an innovative technology aimed at improving public safety, examine its uptake, and explore willingness to pay for safety—particularly with attention to gender differences.
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After
Safety in public spaces is a global concern that can negatively impact individuals’ well-being, cause them to avoid certain activities, and lead to additional expenditures to feel secure. In this study, we document the prevalence of safety concerns and experiences of harassment among university students in the UK. The experiment has three layers of randomization.
First, in the baseline survey, a random subset of students (20%, Round 2 only) receive information about the prevalence of harassment among university students drawn from prior survey evidence. Second, all students are invited to download the safety app with randomized monetary incentives (£0 or £25). Third, among students who download the app, half are randomly assigned to receive a real-time video-call feature connecting them to a trained operator available 24/7, while the other half receive the same app, without the video-call feature.
The study is conducted in two rounds: Round 1 (Spring 2025) and Round 2 (Spring 2026). A supplementary Prolific study (N=600 UK university students) collects additional demand and travel data. Endline surveys are conducted approximately 2-3 months after baseline. We study effects on crime experiences, perceived safety, beliefs about crime risk, anxiety, and mobility. We characterize selection into adoption, and study how effects vary across individuals. We additionally estimate willingness to pay for safety and develop a structural model of nighttime travel choices.
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Field
Intervention End Date
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Before
January 22, 2026
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After
September 30, 2026
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Field
Primary Outcomes (End Points)
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Before
1. Safety perceptions (at night alone) - survey data
2. Mobility (time, mode of transport, itineraries, in group/alone) - survey data + admin data
3. (Anticipated) Anxiety walking at night - survey data
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After
Primary outcomes are organized into four families:
Family 1: Transport-related perceived safety (safety walking in public spaces, using public transport, and in a cab/Uber; 1-5 Likert).
Family 2: Anxiety (GAD-7 score and minimal anxiety binary; nighttime walking anxiety intensity 0-10).
Family 3: Beliefs and perceived risk (perceived probability of own harassment in 100 outings; perceived probability on usual route; confidence in own estimate).
Family 4: Activities and mobility. Extensive margin: nights returning home after 10pm, stayed home when wanting to go out. Intensive margin: nights alone, taxi use when alone, share of solo returns by taxi.
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Field
Primary Outcomes (Explanation)
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Before
We will correct for multiple hypothesis testing when necessary. For each family of outcomes, we will construct summary indices and also analyze individual outcomes separately.
1. Safety perceptions (at night while alone) are measured using survey data, specifically six situational questions rated on a 1–5 Likert scale, as well as the question, “When is the last time you were willing to walk alone at night?” We will construct a general index of safety perception, along with separate indices for: (i) safety while walking or using public transport, and (ii) safety across specific types of situations. For analysis, we will transform the Likert-scale responses into binary (dummy) variables.
2. The data here comes from different sources (self-reported data, admin data from the university, and data from the app). Here as well we will construct first a general index of mobility at night, and then analyze each group and outcome separately.
3. Anticipated anxiety (Likert 1-5) and Intensity (1-10) will be reported in their original scale version and dummy version.
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After
For each primary family, we construct a summary index following Kling et al. (2007): components are standardized using the control group mean and standard deviation, then averaged. We correct for multiple hypothesis testing within primary families when examining individual components.
Family 1 index: average of standardized safety scores across three situational items. We report both continuous and binary (safe = 4 or 5) versions. (survey data)
Family 2 index: average of standardized GAD-7 score and nighttime anxiety intensity. (survey data)
Family 3 index: average of standardized own harassment probability, route-specific probability, and confidence. Safety salience frequency is measured in Round 2 only and reported as an individual component, not included in the index. (survey data)
Family 4: we construct separate extensive margin (nights out, binary any night out) and intensive margin (taxi share) sub-indices rather than a single index, as these capture different behavioral responses. (survey + admin)
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Field
Experimental Design (Public)
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Before
The project follows a randomized experimental design involving a sample of university students (both men and women) in the UK. To maximize participation, most of the students are invited to complete a baseline survey during class time and are compensated both for completing the survey and for correctly answering selected questions. At the end of the baseline, students are offered further incentives to download the VIOLA RESEARCH app—a new mobile safety app that became viral in Italy. At the end of the baseline survey, students who consent to location tracking are randomized into two groups. Users sign-up in the app using a unique "tester ID." An endline survey is then conducted two/three months later, either via email or through the app. Survey responses are merged with administrative data to support comprehensive analysis.
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After
The study is a multi-stage randomized experiment among university students in the UK. To maximize participation, most of the students are invited to complete a baseline survey during class time. In Stage 1 (Round 2 only), a random subset of students receive information about harassment prevalence. In Stage 2, all students are invited to download the app with randomized monetary incentives. In Stage 3, among students who download a mobile safety app, half are randomly assigned to receive an additional protection safety feature while the other half receive the basic version. The study is conducted across two rounds with an endline survey approximately 2-3 months after baseline.
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Field
Planned Number of Clusters
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Before
N/A
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After
N/A. Randomization at the individual level.
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Field
Planned Number of Observations
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Before
We aim to survey approximately 10,000 students, although the final number may vary depending on the availability and cooperation of professors and university administration. We anticipate conducting multiple rounds of data collection, subject to funding availability, and will update this pre-registration plan accordingly. Eligible participants are students who (i) are at least 18 years old and (ii) provide informed consent to participate in the study. As of now, we have surveyed 1,111 students.
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After
Across two rounds, we have surveyed approximately 3,600 students (Round 1: 1,100; Round 2: approximately 2,500 across multiple UK universities). A supplementary Prolific study collects additional data from 600 UK university students. Eligible participants are students who (i) are at least 18 years old and (ii) provide informed consent. We may conduct additional rounds subject to funding availability.
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Field
Sample size (or number of clusters) by treatment arms
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Before
50% control group, 50% treatment group.
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After
Info treatment (Round 2 only): 80% control group, 20% treatment group.
Incentives (Round 2): 40% low incentives, 60% high incentives.
Incentives (Round 1): 50% low incentives, 50% high incentives.
Video-call (among adopters): 50% control group, 50% treatment group.
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Field
Intervention (Hidden)
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Before
Safety in public spaces is a global concern that can negatively impact subjective well-being, cause individuals to forgo valuable activities, and lead them to incur additional costs to feel secure. In this study, we begin by documenting the incidence of the problem—highlighting the prevalence of harassment and safety concerns among university students in the UK.
We then evaluate an innovative technological intervention aimed at enhancing public safety, particularly in relation to harassment. Using a randomized controlled trial, we assign students to different versions of a novel mobile safety app. This experimental design, combined with rich administrative and survey data, allows us to estimate the causal effects of the intervention on key outcomes, including perceived safety, crime experiences, mental health (anxiety and PTSD), commuting behavior, time use, and educational outcomes.
We also examine willingness to pay for safety and conduct heterogeneity analysis by gender. In addition, we study selection into participation and the determinants of app take-up.
The project follows a randomized experimental design involving a sample of university students (both women and men). To maximize participation, most students are invited to complete a baseline survey during class time and are compensated both for completing the survey and for correctly answering selected questions. At the end of the baseline, students are offered additional incentives—randomized into high and low incentive groups—to download the VIOLA RESEARCH app, a mobile safety app that initially went viral in Italy.
Students who choose to download the app and agree to location tracking are further randomized into two groups: a Control Group, which receives access to the app with geolocation functionality only, and a Treatment Group, which also gains access to a video-call feature enabling 24/7 connection with trained supporters. Users sign-up in the app using a unique "tester ID." An endline survey is then conducted two/three months later, either via email or through the app. Survey responses are merged with administrative data to support comprehensive analysis.
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After
Safety in public spaces is a global concern that can negatively impact individuals’ well-being, cause them to avoid certain activities, and lead to additional expenditures to feel secure. The experiment has three layers of randomization.
First, in the baseline survey, a random subset of students (20%, Round 2 only) receive information about the prevalence of harassment among university students drawn from prior survey evidence. Second, all students are invited to download the safety app with randomized monetary incentives. Third, among students who download the app, half are randomly assigned to receive a real-time video-call feature connecting them to a trained operator available 24/7, while the other half receive the same app, without the video-call feature.
The study is conducted in two rounds: Round 1 (Spring 2025) and Round 2 (Spring 2026). Round 1 was conducted with N≈1100 with a 50/50 incentive split and no information treatment; the endline was administered to adopters only. Round 2 spans across multiple UK universities (N≈2,500) with a 40/60 incentive split, includes the information treatment, and administers the endline to all baseline respondents. A supplementary Prolific study collects additional demand and travel data. Endline surveys are conducted approximately 2-3 months after baseline. We study effects on crime experiences, perceived safety, beliefs about crime risk, anxiety, and mobility. We characterize selection into adoption, and study how effects vary across individuals. We additionally estimate willingness to pay for safety and develop a structural model of nighttime travel choices.
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Field
Secondary Outcomes (End Points)
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Before
1. Harassment experiences (past two months) - survey data
2. PTSD (PC-PTSD-5) and GAD-7 - survey data
3. Academic engagement, performance, and choices - admin data
4. Trust in different types of interventions/institutions - survey data
5. Beliefs about harassment — We measure participants’ beliefs regarding their probability of harassment and incidence.
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After
Secondary outcomes are organized into four families:
Family 5: Situational safety perceptions (safety along usual route from campus to home, near home, near campus). - survey data
Family 6: Experienced harassment and safety incidents (past two months) - survey data
Family 7: Beliefs on prevalence: outcome of information treatment - survey data
Family 8: . Academic engagement, performance, and choices - admin data - analyzed descriptively and treated as exploratory due to limited coverage.
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Field
Secondary Outcomes (Explanation)
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Before
1. Harassment experiences are measured by asking respondents whether they experienced specific events in the past two months, in order to avoid relying on potentially varying interpretations of the term “sexual harassment.” At baseline, we also include a randomized subsample to which we apply hard garbling techniques, allowing us to estimate average misreporting. We construct a dummy variable indicating whether any incident occurred in the past two months, as well as separate dummies for each specific type of incident. We also report the frequency of sexual harassment.
2. PSTD questions are asked only to people that reported having experienced at least one form of sexual harassment (scale 0-5). GAD-7 we report the dummy for minimal anxiety.
3. Educational outcomes are only for students for which we have admin data:
Class attendance (% of scheduled classes)
Exam performance (0-100 scale)
Engagement (on a 1-4 scale, as reported by class teachers)
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After
1. Family 5 (Situational Safety) index: average of three standardized items — safety along campus-to-home route (1-5), safety near home (1-5), safety near campus (1-5).
2. Family 6 (Crime Experiences): we construct three levels of aggregation. (a) Overall crime index (Kling): average of standardized binary indicators for all incident types. (b) Two sub-indices: a sexual harassment sub-index (unwanted sexual comments, unwelcome staring, someone physically following, sexual exposure, unwanted sexual contact, overt sexual touching, attempt to rape/rape) and a non-sexual crime sub-index (theft/attempted theft, physical harassment, verbal harassment). (c) Individual binary indicators for each specific incident type. We additionally report: a binary for any incident in the past 2 months, as well as separate dummies for each specific type of incident. Harassment experiences are measured by asking respondents whether they experienced specific events in the past two months, in order to avoid relying on potentially varying interpretations of the term “sexual harassment.” At baseline, we also include a randomized subsample to which we apply hard garbling techniques, allowing us to estimate average misreporting. For the garbled subsample, we report garbling-corrected prevalence estimates.
3 Family 7 (Beliefs on prevalence): perceived percentage of female university students in London who experienced sexual harassment in public spaces in the past two months (0-100), and the same for male students (0-100). These beliefs are the direct target of the information treatment, which provides the actual statistics from Round 1 survey. This family is the primary outcome for the effect of information treatment.
4.Family 8: Educational outcomes are only for students for which we have admin data (analyzed descriptively and treated as exploratory due to limited coverage):
Class attendance (% of scheduled classes)
Exam performance (0-100 scale)
Engagement (on a 1-4 scale, as reported by class teachers)
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