I noticed this picture of what seem to be vertical wigwags on Wikipedia, reportedly between Church Stretton and Hereford on the Welsh Marches line (http://en.wikipedia.org/wiki/File:Marshbrook_-_geograph.org.uk_-_279032.jpg). I have seen something very similar on the AHB at Warden, between Haydon Bridge and Hexham on the Tyne valley line.
I presume that it's a vertical wigwag, so how would it work when activated?; would it be a red/yellow/red set that behaves like a normal level crossing light when activated; is it used when sight lines on approach roads are restricted?