Don’t even think about dialing that phone with a free hand.

As of today, put both hands back on the wheel and drive. And if you must talk on the phone, do it with a hands-free headset. It’s the law.

The penalty is $124 — if an officer catches you in the act while breaking some other driving rule. Washington State Patrol will cite drivers for using cell phones only if they see another traffic infraction first —including weaving, failing to use indicator or speeding.

The new law makes holding a phone to your ear while driving a secondary offense — unless you’re calling 911.

Text message instead? No way. That’s already against the law.

According to the Insurance Institute for Highway Safety, motorists using cell phones are four times as likely to get into serious crashes.

The good intentions behind the new law may not help as much as some hope.

A study released in May by the Public Policy Institute of California looked at states with similar cell phone restrictions: New York, New Jersey, Connecticut and Washington D.C.

The study concluded that laws banning cell phone use reduce traffic deaths by about 300 a year, but only in adverse driving conditions, such as wet or icy roads.

Given a choice, officers would prefer people just hang up and drive. Hands-free or not, phone conversations are distracting, said State Patrol Trooper Keith Leary.

“When you pick up a cell phone you are thinking about a number to dial, what you are going to say, as well as driving,” he said.

If possible, park before you talk, Leary said.

“Driving a car should take 100 percent of your attention,” he said.