Yes, it's a classic example of the power and skill of your "unconscious" mind - your consciousness is freed up to do novel work because the drive home is so routine that your unconscious mind can do almost all of the work. Should something change - a traffic jam, a detour, a pedestrian crossing the road - your conscious attention will be called back to the more urgent task which is making a decision about how to handle the driving situation.

It seams interesting to me that what we refer to as the conscious mind is unconscious a third of each day and the part we call unconscious is active 24 by 7.

I'm out of my depth here, but a high-level response:

First, I don't think the "unconscious" part is a single process, but myriad processes, and I'd bet they wax and wane.

Second, the "conscious" part is the part that can reason about itself and think abstractly. I think it would be correct to say it's doing higher level computations. The important part is that this is more costly - it's not optimized because it has to be flexible, so it would make sense that it's resting as often as possible.

So, one high-performance, high-power, general-purpose processor to handle the foreground task, and a bunch of low-power processors for background tasks.

Looks like ARM got it right with its big.LITTLE architecture. :)

The low power processors are not general purpose, they are fpga's, they get trained and then are highly optimized at their task.

And they stay in the brain even when not used. You can ride a bike or play a piano years after stopping.

When I have a deeply engrossing unitary (I.e. not one of five tasks but one task for months) project at work I had better start commuting by train and cut out the driving. I have lost two cars by not doing that. Fortunately no one was hurt. One car I had towed to the work parking lot, and just never thought about it until some time after the project when it turned out the office just had it towed off as unknown junk. The project went well.

Oof, that's kind of scary. Sorry you experienced it, and glad nobody was hurt.

I had a workmate at a gamedev place I worked (so lots of deep technical challenges) who apparently regularly missed the motorway exit for work because he was thinking about what he was working on.

I guess the point is even if the distraction is 100% internal you should still do your best to pull yourself out and get your focus back on the road.

The way most people refer to this is "driving on autopilot."