CLARKSVILLE, Tenn. -- It's a law designed for safety: no texting while driving.

"Looking down for any kind of time is very dangerous because you can have a crash," said Sgt. Jimmy Brown.

But law enforcement officials said the new law isn't doing much good so far.

"It's such a hard law to enforce," said Brown.

First, it's difficult to spot. Channel 4 drove around with Montgomery County sheriffs deputies Tuesday, and while plenty of people were seen cruising sans seat belt, no one was caught texting behind the wheel.

"You have to watch what they're doing with their hands, where they're looking, and you can also tell by the way they're driving," said Brown.

It's also tough to prove, especially since there is gray area: Texting is forbidden, but dialing is perfectly legal.

"Knowing that you have a probable cause, that that is exactly what they were doing and they wasn't doing some other thing, like dialing a phone number," said Brown.

Many drivers have learned to outsmart the law. They can drive with their knees and text down low so that no one catches them in the act.

"There's always going to be people that try to do things to get away with breaking the law, and there's always going to be officers out there that find other ways to watch for it, to enforce it," said Brown.

So far, Clarksville police have issued one citation. Montgomery County sheriff's deputies have issued zero. But they don't plan to stop searching any time soon.

"It's going to take time, just like any new law, to get the officers trained and up to speed on what to look for," said Brown.

Eight states have banned texting while driving, and another nine have imposed partial bans that apply only to young drivers.

A first offense in Tennessee costs the offender $50.

Popular Slideshows On WSMV.com:

20 Internet Acronyms All Parents Should Know

Billionaires Top Forbes' Richest List

Tennessee's Most Powerful People Named

Celebrity Mug Shots