SALT LAKE CITY – The number of people stopped for texting while driving on Utah’s highways has increased sharply since lawmakers expanded the law to ban dialing phones or checking email behind the wheel, according to new numbers from the Utah Highway Patrol.

Troopers pulled over 692 people during the first six months after the law went into effect in May. That’s a fourfold increase over the six-month period from May to October last year, when 166 people were stopped.

Most of the 2014 stops came after troopers pulled up alongside drivers and saw them using the phone, Sgt. Todd Royce said.

David Strayer, a University of Utah professor who studies distracted driving, said the increase shows the law is working. The risk of a crash starts to increase when drivers take their eyes off the road for 2.5 seconds, he said. The average text message takes 4 seconds to type. Strayer said people in their 30s and 40s are more likely to text and drive than younger drivers, who have been consistently and emphatically told to keep their fingers off the phone.

Kara Macek, spokesman for the Governor’s Highway Safety Association, called handheld bans a step in the right direction but said all cellphone use behind the wheel is distracting.

“We prefer that people just don’t use their phones when they’re driving regardless,” she said. Even talking on hands-free devices can be distracting, she said.