Barnsdale Road (A656)
Allerton Bywater
North Eastern Railway
Leeds & Castleford Branch
It's the road from Castleford, via 'Peckfield Bar' (where A63 crosses it), to HookMoor, where it rejoins the A1...…… having left it, following the old Roman Road, at Barnsdale Bar (south of Pontefract)
I use this road a lot, but have never seen the mark before, as usually I'm in traffic, but today the Sun was catching it, & it was a relatively traffic-free time of day (circa 12:50 - 13:00)
Looking west off the bridge, to the previous site of the station
Looking up 'Barnsdale' towards
Mary Pannnal Hill
The site of Ledston Station, seen if you scroll down to the correct section here (3rd photograph. below maps);
http://www.lostrailwayswestyorkshire.co.uk/Castleford Garforth.htm
The bridge forms the crest of the hill;
http://www.geograph.org.uk/photo/258895
Looking east, towards the Aire flood-plain;
http://www.geograph.org.uk/photo/121899
Which was crossed on this bridge, now extremely rickety (& not used);
http://www.geograph.org.uk/photo/2869303
EDIT @ 17:23
What is interesting, is that the 1905 (25" - mile) OS map shows the mark on the opposite parapet