What does the checkerd white and red railway sign mean?

Question

I live in the UK and I use the train alot to get to work. What are those red and white checkerd signs that you find on bridges that go over the railway and tunnels mean? They have 2 red and 2 white squares on them. I had this question in my head for more than a week, because there is nothing to do on the way.

Thanks

Answer 1

Limited safety clearance, warning those working on the track that in the event a train passes they won't be in a place of safety.

Answer 2

Gerbil is spot on with his answer. You can also see these signs upon lineside or signal post telephones, in these situations you may only use the telephones if you train offers you protection from danger (i.e. if the "limited clearence" is in relation to the line which your train occupies)

Answer 3

gerbil is word perfect

Answer 4

It means Limited Clearance, and the official definition is: 'a place where there is not enough room to walk or stand between a moving train and trackside infrastructure.'