Researchers have longtime warned about the effects of cell phones on driving performance, whether it involves talking to someone or texting a message. Some could argue that talking to another passenger in the car may be just as distracting, but a recent study by researchers at the University of Utah shows otherwise.

They took into consideration the effect of cell phone use on the three levels of performance identified in drivers: the operational or control level, which involves keeping a vehicle on a predetermined course, the tactical level or behavior, which involves maneuvering the vehicle in traffic, and the goal-directed level, which refers to executing navigational tasks.

Talking to a cell phone and driving at the same time was shown to have a negative effect on the first level of performance, by lowering the lateral control, often leading to drifting on the side of the road. On the second level of performance, cell phone use led to changes in speed, acceleration, and delayed reaction times.

The current study analyzed the third level of performance in particular, due to a lack of evidence to prove the effect of cell phones on performing navigational tasks. With the help of a simulator, the researchers studied the performance of drivers talking on a cell phone compared to drivers using an adaptive cruise control system.

The conclusion was that talking to a cell phone while driving can lead to reduced driver situation awareness and increase the perceived mental workload relative to no phone and adaptive cruise control conditions.

So why are cell phones more distractive than chatty passengers? “The passenger adds a second set of eyes, and helps the driver navigate and reminds them where to go,” psychologist David Strayer of the University of Utah explained.

The study found that although in both cases, the driver is having a conversation, drivers talking on a cell phone almost always missed an exit, compared to drivers talking to a passenger, who almost always took the exit.

“The difference between a cell phone conversation and passenger conversation is due to the fact that the passenger is in the vehicle and knows what the traffic conditions are like, and they help the driver by reminding them of where to take and exit and pointing out hazards,” Strayer said.

A previous study by University of Utah researchers revealed that drivers talking to the their cell phones became distracted, made fewer lane changes, and drove 2 to 3 percent more slowly in medium and highly congested traffic. The warning about the effects of cell phone use while driving includes headsets as well, scientists say.

In July this year, the Wireless Telephone Law which prohibits the use of wireless phones while driving took effect in California. The law was divided into two, for under 18 and over 18 drivers, making a special provision for younger drivers, prohibiting them from using any type of device while driving, whether for talking or for text messaging.

According to the California Highway Patrol, statistics have placed young drivers as the most vulnerable to driving distractions such as talking with passengers, eating or drinking, and talking or texting on wireless phones, which increases their chance of getting involved in car accidents.