...Because earplugs are fatally boring on long drives and you still hear mechanical noises...

I bought a pair of Active noise cancelling headphones and must say that I like em.

Active noise cancelling doesn't work very well on the train because you can still hear people but it does reduce all the droning and mechanical clatter sounds of the car. You can still hear when to change gears or the growl when you mesh it into the floor. ... and you have music.

$70 well spent.

Hope you aren't wearing these whilst driving?

Mmmmm, can you hear emergency sirens and car horns?

Deaf people are allowed to drive so I can't see there's much of a problem except looking with cans on in the car.

Oh

Theoretically you should hear horns and sirens better than through earplugs because the noise cancelling works best in lower frequencies.
For $70 you also won't get better than 90% reduction anyway.