WASHINGTON — Texting while driving increased 50 percent last year and two out of 10 drivers say they’ve sent text messages or e-mails while behind the wheel despite a rush by states to ban the practice, the National Traffic Safety Administration said today.

An annual study conducted in 2010 by the National Highway Traffic Safety Administration of drivers observed at selected stoplights and intersections found that at any given time just under 1 percent were texting or manipulating hand-held devices, such as using a Web-capable smart phone or cell phone to view travel directions, check e-mails or calendar appointments, or surf the Internet, manual dialing, playing hand-held games, and holding phones in front of their faces. But the activity increased to .9 percent of drivers, up from .6 percent the previous year.

The share of drivers speaking into headsets was also .9 percent and had increased by the same amount. But drivers talking into hand-held cell phones remained flat at 5 percent.

Eighteen percent of drivers said they’ve sent text messages or e-mails while driving, according to the results of a national telephone survey by NHTSA of over 6,000 drivers aged 18 or older. The survey was conducted a year ago and released this morning. Among drivers 21 to 24 years old, half said they’ve texted behind the wheel.

The survey also found that most drivers will answer a phone call while driving and most will continue to drive after answering.

The increase in text-ing while driving came despite a rush by states to ban the practice. Last month, Pennsylvania became the 35th state to impose a ban. Mississippi has no ban.

The increase in texting while driving is alarming, said Jonathan Adkins, a spokesman for the Governors Highway Safety Association.

“It is clear that educational messages alone aren’t going to change their behavior,” Adkins said. “Rather, good laws with strong enforcement are what is needed. Many drivers won’t stop texting until they fear getting a ticket.”

The safety administration reported this year that pilot projects in Syracuse, N.Y., and Hartford, Conn., involving stepped up ticketing coupled with high-profile public education campaigns produced reductions.

Before and after each enforcement wave, NHTSA researchers observed cell phone use by drivers and conducted surveys at driver licensing offices in the two cities. They found that in Syracuse, hand-held cell phone use and texting behind the wheel declined by one-third. In Hartford, where researchers initially identified drivers talking on their cell phones at twice the frequency, there was a 57 percent drop in hand-held use and texting behind the wheel dropped by nearly three-quarters.