Discrimination Against Free Riders: Unintended Consequences of Free Buses for Women in Delhi

Last registered on September 09, 2026
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Pre-Trial

Trial Information

General Information

Title
Discrimination Against Free Riders: Unintended Consequences of Free Buses for Women in Delhi
RCT ID
AEARCTR-0019562
Initial registration date
September 02, 2026

Initial registration date is when the trial was registered.

It corresponds to when the registration was submitted to the Registry to be reviewed for publication.

First published
September 09, 2026, 3:45 PM EDT

First published corresponds to when the trial was first made public on the Registry after being reviewed.

Locations

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Primary Investigator

Name
Laura Montenbruck
Affiliation
Stockholm University
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Other Primary Investigator(s)

PI Name
Girija Borker
PI Affiliation
World Bank
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PI Name
Cristina Cibin
PI Affiliation
Heidelberg University
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Additional Trial Information

Status
In development
Start date
2026-10-01
End date
2027-04-30
Keywords
Behavior, Gender, Labor
Additional Keywords
Gender discrimination, public transport, affirmative action, female mobility, field experiment, India
JEL code(s)
J16, J71, R41, H42, O18, C93
Secondary IDs
Prior work
This trial does not extend or rely on any prior RCTs.
Abstract
Across the developing world, women face mobility barriers that constrain access to jobs, education, and social networks. Gender-targeted transport policies, such as Delhi's Pink Ticket Scheme, which grants women free bus travel, aim to ease these constraints but may generate unintended consequences at the point of delivery. We study whether free fares lead bus drivers to discriminate against female passengers, raising the effective cost of travel for the very group the policy targets. Descriptive data show that buses fail to stop for women roughly 50% more often than for men. Combining a mystery shopper field exercise with a lab-in-the-field experiment with bus drivers and conductors, we causally identify discriminatory non-stopping behavior and decompose its underlying mechanisms, distinguishing among gender norms, fairness concerns, economic incentives, and safety considerations. The findings will inform the design of inclusive public transport systems in low- and middle-income countries.
External Link(s)

Registration Citation

Citation
Borker, Girija, Cristina Cibin and Laura Montenbruck. 2026. "Discrimination Against Free Riders: Unintended Consequences of Free Buses for Women in Delhi." AEA RCT Registry. September 09. https://doi.org/10.1257/rct.19562-1.0
Sponsors & Partners
Experimental Details

Interventions

Intervention(s)
Intervention Start Date
2026-10-01
Intervention End Date
2026-10-31

Primary Outcomes

Primary Outcomes (end points)
Mystery shopper exercise:
- Indicator variable: Bus did not slow down
- Indicator variable: Bus did not stop
- Indicator variable: Bus did not stop in designated area
- Indicator variable: Mystery shopper is unable to board
- Continuous variable: Total waiting time before successfully boarding a bus

Lab-in-the-field experiment:
- Indicator variable: Driver does not stop
Primary Outcomes (explanation)

Secondary Outcomes

Secondary Outcomes (end points)
Mystery shopper exercise: /

Lab-in-the-field experiment:
- Continuous variable: Time to decision
Secondary Outcomes (explanation)

Experimental Design

Experimental Design
To identify gender-based discrimination in the usage of public buses, we conduct a randomized field experiment that generates exogenous variation in whether a male or female passenger is waiting at a bus stop in Delhi. We deploy male (control) and female (treatment) mystery shoppers, recruited to be comparable across all visible characteristics, to bus stops across a sample of routes in Delhi. Shoppers are recruited according to a set of predefined types, each a combination of age, marital status, religion, and SES, chosen to reflect real bus users. We hold these differences fixed across gender, so that any difference in outcomes between male and female shoppers can be attributed to gender. During the exercise, mystery shoppers wait for the bus and, for each passing bus of their assigned route, record variables indicating the bus's stopping behavior. We use these variables to investigate gender-based differences in stopping behavior and ability to board.

We complement the mystery shopper exercise with a lab-in-the-field experiment designed to identify the potential reasons behind the discriminatory behavior we document in the field. Bus drivers play an incentive-compatible game in which they take on the role of a driver completing his shift. To isolate the motives that drive discriminatory behavior, we vary the environment in which they make their stopping decisions.
Experimental Design Details
Not available
Randomization Method
Randomization done in office by a computer
Randomization Unit
Mystery shopper exercise: Route segment s on route r on day d in time slot t

Lab-in-the-field experiment: individual i in round r at stop s
Was the treatment clustered?
Yes

Experiment Characteristics

Sample size: planned number of clusters
Mystery shopper exercise: 120 route-segments

Lab-in-the-field experiment: /
Sample size: planned number of observations
Mystery shopper exercise: 7,200 bus passings Lab-in-the-field experiment: tba
Sample size (or number of clusters) by treatment arms
Mystery shopper exercise: 3,600 bus passings per gender

Lab-in-the-field experiment: tba
Minimum detectable effect size for main outcomes (accounting for sample design and clustering)
Supporting Documents and Materials
IRB

Institutional Review Boards (IRBs)

IRB Name
IRB Approval Date
IRB Approval Number
Analysis Plan

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