Wig-wag red lights on the track

[Ken H]

Travelling to Settle late one night recently, I noticed a set of red wig wag lights low on the track just North of the Settle Junction down starter. I am sure Settle Jct box was closed when I went past, but I was driving so didnt get a proper look.
What are these for? Are they a permanent installation? I assume the line was closed at the time. Didnt see any on the Morecambe line, but its behind the S&C embankment there
thanks

 

[edwin_m]

A Work Site Marker board sounds the closest - but it has two red lights flashing in phase not alternating. A possession limit has one red flashing light. See 30.3 and 30.5 on the link below.

Signs for Engineering Possessions (railsigns.uk)

 

[Supercoss]

Work site marker boards ( different types in use including minature ones)

http://bed-pan.homestead.com/markerboard.jpg

PLB " Stop" board ( Possession Limit Board) - again different styles in use including lightweight stick

http://bed-pan.homestead.com/markerboardsplbshort.jpg

 

[CAF397]

A Work Site Marker board sounds the closest - but it has two red lights flashing in phase not alternating. A possession limit has one red flashing light. See 30.3 and 30.5 on the link below.

Signs for Engineering Possessions (railsigns.uk)

Highly likely a PLB on each line flashing alternatively, so at night it would give a wig wag effect?

 

[Ken H]

Highly likely a PLB on each line flashing alternatively, so at night it would give a wig wag effect?

ah. Never thought of that!