Hands free phones aren’t any safer for drivers than hand held phones according to research from Carnegie Mellon University.

Cars are becoming more and more connected to the web with dashboard screens that essentially act as a built in smartphone with many of the features seen in a typical computer. Auto manufacturers say they’re providing what the customer wants but, while cars are being made safer in other areas, the addition of these web connected devices are creating the potential for even more distracted drivers on the road. The manufacturers are also pushing the idea that hands free phones and texting are safer than using handheld devices but the scientific evidence doesn’t back that up.

In 2008, the Carnegie Mellon Center for Cognitive Brain Imaging published a study that used brain imaging to see what actually goes on in the brain while a driver is engaged in a phone conversation.

To conduct the study, 29 volunteer subjects “drove” over a simulated driving course while inside an MRI brain scanner. The subjects had to maintain speed while steering along a winding course. For the first test, the test subjects drove the course without any interruptions. In the second test, the subjects had to drive the course while listening to and answering true or false questions.

While driving without interruptions, the area of the brain that showed the greatest activity was the area responsible for “spatial awareness”; the area of the brain most associated with the complex task of safely steering a car

When the subjects had to listen and answer questions while driving, the activity in the brain’s spatial awareness area was reduced by 37 percent and the area of the brain associated with language comprehension showed the greatest activity.

In spite of all the modern day hubbub about the ability to multitask, the results of the study convinced the researchers that the brain itself isn’t capable of multitasking. The brain has to ignore other demands in order to do one task effectively.

If someone is using a phone while driving, whether it be a handheld or hands free phone, the brain is concentrating on the content of the call, not on the task of driving. When activity in the area of the brain responsible for steering a car and watching the road is reduced, it can be easy to miss a potentially hazardous situation ahead and that can lead to tragedy.

Other, more recent studies have shown that voice activated phone and texting systems such as Apple’s Siri or Google’s voice activated search can be even more distracting than using a hand held phone because of the frustrations experienced when the system fails to understand your requests. Studies also show that the distractions of smartphone notifications, even when they aren’t answered, can lead to driving mistakes.

The best advice for drivers who want to complete their trip safely is to turn off the phone while driving and, if a call must be made, pull off of the road.

Read more: Carnegie Mellon Study Shows Just Listening To Cell Phones Significantly Impairs Drivers