Public Transport Etiquette
Rule 2: Bodily Contact When Sitting Side by Side

When sitting next to someone ensure that the least possible amount of body contact is made. Upper hip is just about acceptable. Whole length of thigh starts to feel a little familiar. More than 3 points touching (for example, upper arm, hip and thigh) is distinctly uncomfortable. Try not to trap your neighbour's leg skin as you sit down - if you sit on someone you are too close.

Likewise with standing - don't rest your book, bag, newspaper or arm on the head, neck or shoulder of the person sitting below you. Don't knock them with your rucksack as you turn around. Don't let your body hang into their personal space.