Even when it is nailed down

It can be stolen in South Africa;

Metal thieves in South Africa have stolen nearly 10km (6 miles) of working railway track, causing about $2.3m (£1.3m) of damage, it's emerged.

Chunks of track were stolen over the course of several months from a line used to take trains from Johannesburg to a depot in the town of Nigel....

...says ...[raidlway spokesman] Mike Asefovitz ... "These aren't the little guys. To take this kind of weight and to cut it up you need specialised machinery." The stolen rails are reportedly worth about $120,000 on the scrap metal market.

The theft has left 34 brand new train cars stuck at the maintenance plant just as they were due to be put into use, and the depot now fears for its future with about 700 jobs potentially at risk. In South Africa, metal theft is a serious problem costing the economy hundreds of millions of dollars a year.

Hard to believe that there isn't a way to detect, and stop, such thieving.