Flashing white strobes, trackside?

[ShampooEfficient]

I regularly drive parallel to a railway line, which for the last few weeks has had a couple of flashing white strobes, mounted on a yellow and black chequered plinth, next to the track... probably a really boring question but what are they for?

[mrmaggit]

If it is a rectangular board in yellow with two full chevrons in black, with the lights in the upper part of each chevron, it is an emergency speed restriction ahead warning sign.

If it is a rectangular sign in yellow with a black number on it, it is a temporary speed restriction warning sign, with the speed being the numbers. An "R" on it means repeater.

[ShampooEfficient]

First one sounds right! Ta chap!