MISSOULA -- An ordinance banning text messaging while driving and bicycling is now in effect in Missoula.

A month ago, the western Montana city adopted a new ordinance restricting all cell phone use while driving. The law also banned talking on your cell phone while behind the wheel, but Mayor John Engen vetoed that section.

What remains, and went into effect July 1, is the ban against texting while driving or biking. That includes sending e-mails. Police Chief Mark Muir says officers can pull over a driver they believe is punching out a message.

The fine for a first-time offender is a minimum $100 and a maximum $500. The minimum fine for a second offense within a year is $150. And if you cause a crash as the result of text messaging, the fine is a minimum $350.

Knowing whether the person is dialing a phone number or texting is obviously tricky, Muir admitted.

''That's the big question people have,'' he told the Missoulian newspaper.

It's a question that probably won't be answered until the new ordinance is challenged in court.

''As time goes on and individuals are cited, the courts will help us sort out some of the details,'' he said.

Crash data collected up to this point never distinguished between drivers talking or texting on their cell phones at the time of an accident, Muir said. Now, based on citations, police will be able to keep more accurate data.