A new mobile site has been ceated. Whilst this page will remain you may find Trainspots mobile better suited to a smart phone.

From the M74 - Junction 9:
Take the B7086 (Lanark) and continue along until Auchenheath. Then Join the A72 and travel in the Lanark direction until the junction with the A73 at Kirkfieldbank. Here follow the signs for Carlisle through to Lanark. In Lanark join the A70 and this will take you to Carstairs Village. In the village turn right down Carstairs Road, this will take you past Carstairs station. Continue down this road just over half a mile till you come to the church. Turn right at the church into Pettinain Road and continue straight along this road.
After another half mile you will cross the River Clyde, continue along and when you get to the top of the steep hill which is about another three quarters of a mile you will see a dirt track leading down to the line side and this track takes you right along to the bridge.

You will need to leave your car at the top of the hill and climb over a gate to access the dirt track.

The location is best reached via Carstairs which is difficult to get to by public transport, but it is possible. There is a limited train service from both Edinburgh and Glasgow by both ScotRail and Virgin XC.
Alternatively, it's possible to get the train to Lanark and then the bus to Carstairs

ScotRail train times for Lanark
Bus Timetable - William Stokes
Bus Timetable - Irvines
Travel Scotland Journey planner

Once at Carstairs then follow the road directions.

It's a field, the nearest public amenities are back in Carstairs.

scot-rail.co.uk

There's not much shelter here, so when the sun is out, you need to keep it on your back. For southbound trains (and going away shots of northbound trains), the sun will be on your back from mid morning, for northbound trains you will need to wait until the sun swings round after lunch.
A long telephoto lens is highly recommended, as you can see the line for almost a mile to the north as it crosses the flood plain before reaching the viaduct. The viaduct it's self is reasonably picturesque although the sides obstruct the view a little.
As this spot is fairly remote, there is no traffic noise to interfere with taking videos.

One final point to note, there is OHLE, but it is reasonably spaced for taking photos between the masts. The line speed over the viaduct is 100mph, although services from the Edinburgh direction will still be accelerating up from 20mph at Carstairs South Junction.

Carstairs
Ravenstruther