I'm reading a book which you should read, too.
Tom Vanderbilt's Traffic: Why We Drive the Way We Do (and What It Says About Us). (Click on the title to see the book at amazon.com. I've never made money from this site, but I think I might make a few cents if you happen to order the book through this link.)
This book is about the psychology/sociology of driving. Maybe even the anthropology of driving. It's endlessly fascinating.
I just finished a section on attentional processes involved in driving. Vanderbilt points out that very inexperienced drivers have to focus almost all the attention they have to the most fundamental aspects of driving. Like, steering the car so that it stays in the lane and making sure one's feet are operating the correct pedals, and putting the right amount of pressure on the right pedals at the right time. If we close our eyes and take a deep breath, we can remember those earliest driving experiences, with Mom or Dad in the front seat with us. We really had to focus on that center line and that line at the curb and where were our feet anyway?
With experience, through the process psychologists call "overlearning," those most basic driving operations become largely unconscious and automatic for us. Experienced drivers can drive all over town and not have much, if any, conscious awareness of adjusting the position of our cars within the lane markers. We never have to focus on moving our feet from pedal to pedal. It's all autopilot, so to speak. That's good news, because it frees up more of our finite amount of focus, attention, and information-processing capacity for other matters, hopefully driving-related.
I think of it this way. We only have so much "bandwidth" for attending to stimuli, processing information, and motor coordination when we are driving, just as a computer only has so much memory and so much processor power. Inexperienced drivers need to devote much more of this finite bandwidth to the most basic driving functions. Keeping the car on the road, not running into other cars, etc.
This is why very new drivers-in-training will often be unable to regulate the vehicle's speed. We have to point out their speed to them. You're going too fast. Now too slow. (But it seems like it's mostly too fast!) Novice drivers don't have enough bandwidth to be checking their speed as they go.
A related idea: New drivers, says the research cited by Tom Vanderbilt, focus more on the road directly ahead and for a shorter distance from the front of the car than do experienced drivers. They use more "fovial" vision and less peripheral vision.
This is why distractions, like passengers in the car, are even more problematic for new drivers than experienced drivers. Anything that the new driver pays attention to (the radio, the friends in the car) crowds some of the limited bandwidth, leaving less for essential driving skills like watching for other cars, anticipating the paths of other vehicles, regulating speed, reading signs, and so on.)
Like most of us, as they gain more experience, they can "automate" some of the basic functions and that frees up more attention and focus to deal with othe aspects of driving and even some of the distractions we all encounter.
But for all of us who drive, I think the real insight here is that the attention we pay to non-essential things when driving (our Blackberrys, GPS devices, CD players, putting on make-up, eating, drinking, etc.) MUST reduce the attention and focus we have available to drive safely.
Anyway, grab a copy of Tom Vanderbilt's splendid book. It's informative and actually quite entertaining.