Longer-term effects of Washington, DC, law on drivers' hand-held cell phone use

To determine whether the substantial short-term declines in drivers' use of hand-held phones achieved in the District of Columbia (DC) were sustained 1 year after a ban.

Drivers' daytime hand-held cell phone use was observed in DC and nearby areas of Virginia and Maryland, states without bans. Observations were conducted several months before the ban, shortly after, and 1 year later. The number of vehicles observed in all three surveys combined was 51,945 in DC, 36,796 in Maryland, and 43,033 in Virginia.

The rate of talking on hand-held phones declined significantly from 6.1 percent before the law to 3.5 percent shortly after; when measured 1 year later, use was 4.0 percent, still significantly lower than baseline. Based on increases in rates of talking on hand-held phones in Maryland and Virginia, longer-term phone use in DC was estimated to be 53 percent lower than would have been expected without the ban. Declines in DC were identified for drivers of vehicles registered in all three jurisdictions.

In DC, there was an initial decline of about 50 percent in drivers talking on hand-held cell phones following a ban, and this decline was sustained about 1 year later. After a similar ban in New York, there was an initial decline in phone use comparable with the initial decline in DC, but the decline a year after the New York ban took full effect was only about 21 percent and not statistically significant. The potential difference in sustained effectiveness for the DC ban may reflect tougher enforcement in DC. Even if full compliance with hand-held phone bans can be achieved, the risks from drivers' use of hands-free phones will remain.