New Hampshire is my beloved home state, and its highways have gotten a recent facelift. They've recently installed high-speed tolls at toll stations throughout the state, as well as large LED signs, holstered high above the interstates, proclaiming rhymed warnings to commuters: "Don't text and drive. Arrive alive" and "Drive sober or be pulled over."

I support these causes, but I'm having a harder time getting behind New Hampshire's newest highway catch phrase: "Hands free, a better way to be." Without context, this sounds a bit like a call to drive with no hands, much like that unfortunate no handlebars song from my high school era. But a different message is at the heart of this tune: NH has followed the lead of several states and banned handheld cell phone use while driving, and I think that's kind of bullshit.

Now I don't talk on the phone when I drive, and I don't think it's safe to do so. But here's the thing: holding a piece of plastic up to your ear isn't the primary cause of cell phone related car accidents. To be clear: I am not defending cell phone use while driving. I'm simply calling foul on these "hands free" laws because the research overwhelmingly says so.

Cognitive load & driver distraction

Cognitive load is the amount of strain on your working memory; it's the culmination of the mental taxation on your processing capacity at any given time. No matter how "good of a multi-tasker" one might claim to be, we all have a limited pool of cognitive resources. Every task we perform takes up a portion of this limited pool. Unsurprisingly, the more challenging the cognitive task, the greater the cognitive load. And the more thinly stretched our cognitive resources are, the more prone we are to error.

Driving induces a certain cognitive load. Driving on a quiet country road is less mentally onerous than driving on a three lane highway, which is less onerous than driving through Harvard Square at rush hour. Having a conversation also induces a cognitive load; chatting about your day with your mom is less taxing than is delivering a pitch to a potential client.

There are three possible modalities for distracted driving. We can basically summarize distracted driving as anything that takes your:

Eyes off the road (visual)
Mind off the road (cognitive) or
Hands off the steering wheel (manual)

So yes, hands-free mobile devices do remove the manual aspect; drivers can have both hands on the wheel if they aren't holding mobile devices (although 47% of drivers reportedly drive with one hand "regularly" regardless). But all distractions (visual / manual / cognitive) are not created equal. Let's take a peak at some research.

A correlational study conducted in 2010 at the University of Alabama, Birmingham concluded that among 110 college students (averaging 20 YOA), there was no statistically significant difference in the number of accidents incurred by drivers using hands-free vs handheld mobile devices in the car.

Empirical research also backs up these correlational findings. This literature review, published in 2009, compiles findings from numerous empirical studies on the matter and concludes that the data overwhelmingly suggests a significant safety threat imposed by talking on a cell phone while driving, regardless of the interface. In fact, majority of the studies they review showed no statistical difference between subjects using a hand-free versus a hand-held device. Perhaps even more shocking is that the results from a 2013 study suggest that driving while talking on a cell-phone—regardless of interface—was comparable to driving drunk.

From the research, it appears that it is not the manual task of holding a phone that distracts drivers, but rather the cognitive task of holding a conversation with the person on the other line. And the more demanding that conversation is, the greater the risk. Notably, having passengers in the car does not present the same mental onus. Adult passengers tend to take cues from the driving situation, and can alter their behavior in the car to avoid distracting the driver during a complex driving task. Furthermore, passengers act as a second set of eyes, scanning surroundings and providing insight. In most cases, they are a passive aid to the driving task, rather than a detriment.

The big picture

Given everything presented here, coupled with being a reasonable person, I would never argue that talking on a handheld mobile device while driving is safe. I can even see *some* benefit in talking on a hands free device, despite what the majority of the research in the aforementioned studies suggests (although, when push comes to shove, stat sig @ p > .05 or it didn't happen). My point, though, is that we're lying to people. "Hands free, a better way to be" is effectively telling Granite Staters that talking on their cell phones is safe as long as they use a hands-free system. As these systems become standard on more and more vehicles, taking a conference call while sitting in traffic will become a norm, and people will be disillusioned into thinking it's a perfectly safe thing to do.

Hands-free mobile devices are kind of like margarine: a whole lot of fuss, and—spoiler alert—still bad for you. Rather than misleading the public into believing that "hands free [is] a better way to be," let's put our resources toward educating them about the true, statistically robust findings regarding cell phone use while driving. It might not be the legislative iron fist that we seem to require to denote progress, but at least it wouldn't actively promote behavior that is still destructive. The hands-free legislation is a well-intentioned attempt to solve a legitimate problem that is costing lives. But in reality, we're only breaking down the strawman. If we're not attacking the root cause of the problem—the cognitive act of speaking on the phone, as opposed to the manual act of holding the phone—it's only going to get worse.