If a driver looks, can they really fail to spot a motorbike? Yes, and research has highlighted a number of reasons why:
If you are sat at a junction waiting for a gap in the traffic, ask yourself if your field of vision is clear. A motorbike projects a very narrow image as it approaches and if you only take a quick glance to see if it's safe to pull out, it can easily be masked from your view by street furniture at a crucial time.
Are there lampposts, pedestrian crossing controls or A-boards outside shops that obscure the view? Are the A Pillars in your car creating a blind spot? This framework supports the roof and can sometimes obstruct your view. Double-check the road: is there a motorbike approaching?
Do my eyes deceive me...?
When you look at a car coming towards you, it is a large, wide block of moving colour. Your eyes become accustomed to spotting objects of this size and shape. That's a problem for motorcyclists as their bikes offer a narrower silhouette that can be hard to pick out against a colourful and busy backdrop. It's so easy to look but not spot the biker. Motorcycles can also be hard to pick out if they are overtaking a larger vehicle, particularly a van or a lorry.
Hiding in plain sight
If a small object moves towards you in a straight line, it's possible for your eye and brain to fail to perceive any movement. The image of the motorbike becomes larger on your retina as it approaches but is not big enough to attract your attention. Literally, you look at the approaching object but don't see it.
It's a phenomenon called motion camouflage. It breaks down as the object gets closer and the image size become larger but by then you may have already decided the way is clear and pulled out in front of an oncoming motorbike.
I've got plenty of time
Even if you spot the bike, you could still be about to cause a crash. Our judgement of the speed of objects approaching us is related to their size - this is known as size arrival effect. Car drivers often under-estimate the speed of a motorbike because of its small stature - and over-estimate the time it will take for it to reach us. So even if you spot a motorbike, be cautious when pulling out: have you really got the time to complete your manoeuvre safely?