manners......driving....

On the ongoing ever expanding subject of 'manners' I am currently on holiday up in Scotland so have hired a car to get about (my tractor was sold when I arrived in London). When people are going left or right should they not, maybe, indicate this intention? Instead it seems that many prefer to keep this information to themselves. Have they sat driving tests? Do they have any road sense? Have they got brains? This aggravates me and causes stress and shouting.