let me give you a real life situation that happenend to me to demonstrate why white at the back is a BAD thing.
whilst travelling through the centre of Ireland - at nightime - ina car with 4 people in it - at reasonably high speed and on a straight, but unlit road.
A car comes the other way, we slow and pass each other.
and again a bit later.
then more white lights ahead,
we're approaching at similar speeds to the last set of white lights
I start to mentally aim to the left - AS USUAL for an approaching car
as we get nearer - FUUUUKKKK !!!!
its a tractor going slowly - no other lights apart from a white spotlight on the cab pointing back to the trailer.
it could have ended horribly by us clipping the verge and heading off to the left, instead of the right.
I'm not making excuses for driving too quickly, but its an automatic reation - as Frank says.