The structures were installed under the project to upgrade and revamp Carstairs Junction.
Part of a phased programme, works at the key junction on the West Coast Main Line is expected to help simplify the track layout to address challenges on the network.
The upgrades will also allow the separation of non-stop passenger and freight trains from those halting at the station.
Work so far at Carstairs is said to entail an investment of over £100m in the junction.
The new sections of track and modern signalling deployment will help improve journeys between Glasgow and Edinburgh, in addition to accommodating the longest freight trains on the network.
The works also included the deployment of new overhead line masts and signalling system.
Under the project, over 3km of track renewals and 1.5km of drainage have been completed, and work related to removing some of the redundant equipment has been started.
As part of the next phase of work in 2023, around 4km of new drainage will be added and further embankment work will be conducted.
The project will also include the installation of 10km of new track.
Network Rail programme manager Jim McCleary said: “We’re now gearing up for the final construction of the new track layout, which includes 10km of track and 27 new sets of switches and crossings, which allow trains to move between tracks.”
Carstairs, which is 26 miles to the South-East of Glasgow on the West Coast Main Line, is a triangular junction that enables a route between Glasgow and Edinburgh and both Glasgow and Edinburgh to the south.