Which takes more concentration, bike or car?

Bike. Need to anticipate far more cos when it comes to bikes so many car drivers look but don't see.

but as a rider driving a car you should be making these same observations (I hope)

Yessir, of course - but so many drivers don't. Meaning that riders have to compensate for it.

This is true! its kinda taught as you learn to anticipate people not seeing you and too pay more attention because of it

Even if road concentration was the same, then there remains machine concentration. Bikes require more skill to operate than a car does.

Also, when riding, if the weather conditions start to make things a bit harder, then we try and make up for it by concentrating harder to supress any creeping mental/physical fatigue.

yeah, i would say riding a bike is certainly more physically tiring

[ethariel]

Having driven a car only a few times (really didnt take to it, maybe because of 10+ years on a bike afore i tried a car) on a bike it's not so much concentration than 'self preservation'.

I just assume everyone in a car is out to get me, that way i'm plesantly surprised I'm a pessamist - i just assume everyone is out to get me......

In a lot of ways i suppose its more of a 6th sense, almost a 'link' at times with the bike, subconciously steering away from possible conflict/issues before you even realise you did it whereas in a metal cage it much more detached (well when you can stay awake in one).