Text-Message Intervention to Reduce Handheld Phone Use Among Drivers

Last registered on January 31, 2024


Trial Information

General Information

Text-Message Intervention to Reduce Handheld Phone Use Among Drivers
Initial registration date
January 25, 2024

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
January 31, 2024, 11:44 AM EST

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



Primary Investigator

University of Toronto

Other Primary Investigator(s)

Additional Trial Information

Start date
End date
Secondary IDs
Prior work
This trial does not extend or rely on any prior RCTs.
we collaborate with a transportation company that provides on-demand car rides and self-insures against traffic accidents its drivers incur. Using drivers’ smartphone sensor data, we can accurately identify handheld phone use (“HPU”) behavior. We sent a simple text message to a random subset of drivers with high HPU. The message called attention to their HPU behavior and reminded them that repeated passenger complaints of unsafe driving could lead to suspension.
External Link(s)

Registration Citation

Jin, Yizhou. 2024. "Text-Message Intervention to Reduce Handheld Phone Use Among Drivers." AEA RCT Registry. January 31. https://doi.org/10.1257/rct.12887-1.0
Experimental Details


We sent a one-time text message to treated drivers with records of frequent handheld-phone-use: ”Our app shows you may be holding your phone while driving. Passenger reports of unsafe driving, like handheld phone use, can lead to suspension.”

Intervention Start Date
Intervention End Date

Primary Outcomes

Primary Outcomes (end points)
Frequency of handheld phone use
Primary Outcomes (explanation)
We hypothesize that the text-message would trigger a reduction in the frequency of handheld phone use.

Secondary Outcomes

Secondary Outcomes (end points)
Driving hours, other risky behaviors such as harsh acceleration.
Secondary Outcomes (explanation)

Experimental Design

Experimental Design
On the intervention day, we pre-selected a 30-minute window (3-3:30 pm EST). All eligible drivers starting a shift during this period are randomized into the treatment group with 50% probability.
Experimental Design Details
Randomization Method
Randomization is done via the company's internal communications systems.
Randomization Unit
Was the treatment clustered?

Experiment Characteristics

Sample size: planned number of clusters
Completed: 467 treated drivers; 508 control-group drivers (including 21 drivers randomized into treatment but unreachable by text message due to connectivity or device issues).
Sample size: planned number of observations
277,649 trips
Sample size (or number of clusters) by treatment arms
Among treated drivers, 81,655 trips were observed after the intervention and 45,362 before. 150,632 trips are observed for control-group drivers.
Minimum detectable effect size for main outcomes (accounting for sample design and clustering)
The probability of rejecting the null hypothesis (if the null is false) exceeds 95% as long as the treatment generates an increase or decrease in HPU frequency of 5.92% (on that day). Pooling across all days, the minimum detectable effect size is 0.85%.

Institutional Review Boards (IRBs)

IRB Name
IRB Approval Date
IRB Approval Number


Post Trial Information

Study Withdrawal

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Is the intervention completed?
Intervention Completion Date
January 21, 2020, 12:00 +00:00
Data Collection Complete
Data Collection Completion Date
March 10, 2020, 12:00 +00:00
Final Sample Size: Number of Clusters (Unit of Randomization)
468 treated drivers and 508 control-group drivers
Was attrition correlated with treatment status?
Final Sample Size: Total Number of Observations
277,649 trips
Final Sample Size (or Number of Clusters) by Treatment Arms
45,362 trips by treated drivers before intervention and 81,655 trips after. 150,632 trips by control-group drivers.
Data Publication

Data Publication

Is public data available?

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Program Files

Program Files
Program Files URL
Reports, Papers & Other Materials

Relevant Paper(s)

Reports & Other Materials