Off the road - Nina Bawden

It's 2040 and Tom's grandfather is scheduled for a Nostalgic Block where he will be 'looked after' for ever.
But Grandfather slips off the road and beyond the Wall.
Tom follows and discovers another world from the regulated, pampered one he has always known.
It's a harsh, but more natural pioneer pre-WW1 life which suits Grandfather, but which both attracts and repels Tom. Both must decide whether to stay in the past or return to the futuristic, modern world in which they belong. They make different decisions and the book builds towards a gripping race to escape the forces that would carry them both back.