Turner-Fairbank Highway Research Center

« back to the list

A longitudinal analysis of the effectiveness of California’s ban on cellphone use while driving

Product Type

Journal Article


Chenhui Liu, Chaoru Lu, Shefang Wang, Anuj Sharma, and John Shaw



Full citation

Liu, C., Lu, C., Wang, S., Sharma, A., & Shaw, J. (2019). A longitudinal analysis of the effectiveness of California’s ban on cellphone use while driving. Transportation Research Part A: Policy and Practice, 124, 456–467. https://doi.org/10.1016/j.tra.2019.04.016


Cellphone use while driving is an increasingly serious threat for traffic safety and is prohibited in many jurisdictions. In California, the use of handheld cellphones while driving has been prohibited since July 1, 2008. Using interrupted time series analysis, this study explores the effectiveness of the ban by specifically analyzing the crashes caused by cellphone usage in California from 2002 to 2014. These crashes were thought to be able to reflect the role of the ban more accurately than total crashes. The ban was found effective in reducing the cellphone usage-caused crashes in terms of both crash frequency and crash proportion. The study also confirms that crashes caused by cellphone use produce more severe outcomes than other crashes. These findings show that the ban on handheld cellphone use while driving plays an important role for improving traffic safety in California. In addition, it is found that the ban motivates drivers to switch from handheld cellphones to hands-free cellphones, but in terms of crash severity, hands-free cellphone usage and handheld cellphone usage do not show significant differences. These findings support a complete ban on cellphone use while driving--not just a prohibition of handheld cellphone use. The study results are expected to provide new insights for future policy-making related to cellphone use while driving.

Available From

Transportation Research Part A: Policy and Practice

Link To Journal Article

Link not available.


Cellphone ban while driving
Handheld cellphone
Hands-free cellphone
Crash frequency
Crash proportion
Interrupted time series analysis

« Back to the List

HSIS Summaries

HSIS Summary Reports are two to eight pages in length and include a brief description of the issue addressed, data used, methodology applied, significant results, and practical implications.

Read More

Research Reports

A variety of research studies have been performed using data from HSIS. Many of the final reports prepared are now available electronically.

Read More

Technical Summaries

Research reports are often summarized in executive summaries, technical briefs, or other abbreviated formats. Included here are those road safety summaries that involved research using HSIS data.

Read More

Safety Analysis Tools

In addition to conducting research, HSIS resources are also used to develop products that can be used by practitioners in the analysis of safety problems.

Read More

Other Projects

HSIS data are sometimes used in research studies that result in other types of finished products, such as dissertations, theses, and conference proceedings.

Read More