A recent University of Washington study found that one driver in 16, or about 6 percent, uses a mobile phone while driving on Seattle streets.

Philip Howard, a UW associate professor of communication, directed a team of undergraduates who observed more than 2,460 drivers using cell phones from Feb. 12 to 28.

Each driver had one hand on the wheel and a mobile phone in the other. Some drivers were making calls; others were texting or otherwise using their phones.

Cell phone usage peaked on Thursdays, Fridays and during afternoon rush hour, when the ratio was one in 13.

Fifty-five percent of drivers using mobile phones were male, and 45 percent were female. Some 30 percent of drivers using phones appeared to be under 25, and in that group, the percentages reversed: females outnumbered males by 57 percent to 43 percent.

Researchers stood at 47 randomly selected major and minor intersections around the city, noting phone use, gender and whether the driver appeared to be 25 or under.

The research, an audit study because actual behavior was systematically observed, was conducted by more than 90 UW students on arterial routes. The students chose random times between 8 a.m. and 9 p.m. In all, they observed 39,787 Seattle drivers.

Just last week, the Washington state Legislature passed a bill that makes it a primary offense to be caught holding a cell phone to your ear while driving, or to be reading, writing or sending text messages.

This legislation strengthens the state’s current secondary offense law for texting and cell phone use while driving, which fines people only if they are pulled over for another driving infraction such as speeding.

According to the bill, which passed in the House with a 60-37 vote, police can fine offenders with a $124 ticket. The infraction will not go on a driver’s record, and dialing a phone is not considered text messaging.

The measure exempts transit and emergency vehicle personnel, as well as anyone who is text messaging or calling and not using a headset to report illegal activity or summon emergency help. People who are using a hearing aid or operating a tow truck are also exempt.

The bill also forbids any cell phone use by a driver with a learner’s permit or an intermediate license, which is given to drivers under 18 years.

Washington is one of six states and the District of Columbia to have passed laws regulating cell phone use while driving but is the only state that currently considers phoning without a hands-free device a secondary offense.

“We wanted to do this study because there has been a lot of talk about driver safety and mobile phone use,” said Howard. “We always notice drivers around us who are talking on the phone and not paying attention to the road. We wanted to find out how many people were doing just that.”

Many studies document ways in which cell phones distract drivers, but there have been comparatively few scientific studies to estimate the number of drivers using phones, according to Howard.

A national study conducted in 2006 found proportions of cell phone use similar to those noted in Seattle.

“It is hard to say if laws on cell phone driving have had much impact so far,” said Edwin Ortiz, a senior history major who is one of the student researchers.

“There are a lot more mobile phone users now than in 2006, and a lot more media attention to accidents caused by cell phone drivers, but the rate of use is still high.”

As additional field observations, the student researchers noted that drivers who used cell phones were almost always alone in their cars.

Drivers who were seen texting and clearly distracted from the road were recorded as using cell phones. Some drivers initiated a task with their cell phone at a stoplight, but ended when the light turned green.

Other drivers were impressive multitaskers. They combined various activities: eating, smoking, using cell phones, driving with pets in laps or putting on makeup.

When the study was finished, the 90 students were asked about their own use of cell phones. More than two thirds reported that they regularly use their phones while driving.

For the complete study, go to http://www.com.washington.edu.