An eastern Iowa police department plans to use plainclothes officers in unmarked cars to spot drivers violating the state’s new texting-while-driving ban.

Dubuque Police Lt. John Digman told The Telegraph Herald that the policy will start this fall.

The new law, which took effect July 1, allows police to pull over drivers because they’re suspected of texting. Previously, texting citations could only be made in addition to a different reason for making a traffic stop.

The law prohibits drivers from using cellphones or handheld devices to write, view or send messages, play games or browse social media or the internet while driving. However, drivers can use devices for GPS purposes, to make phone calls and to receive emergency traffic or weather alerts.

Officers must have the owner’s consent or a court-issued warrant to search a device. Phone search warrants to prove texting or distracted driving are usually only issued during investigations of a serious crash, said Dubuque County Sheriff Joe Kennedy.

Delaware County Sheriff John LeClere said the specifics make the law difficult to enforce.

“It’s just hard to see inside a passenger vehicle to see exactly what a driver is doing,” LeClere said.

Iowa State Patrol has had troopers post as construction workers or in plainclothes riding in an RV, said trooper Alex Dinkla.

“(The troopers) had a video camera, and as they were driving down the interstate and people would pass them, they would gather evidence on the tapes (of people illegally using their phones) that could be used in court,” Dinkla said.

Troopers made 17 traffic stops in a three-hour period. They issued five citations and two warnings for texting, he said.