The Midland Main Line (MML) improvement will reduce the journey times and increase the passenger capacity. Credit: Network Rail.
The MML electrification on Kettering and Corby section was completed in November 2019. Credit: Network Rail.
The bridges and viaducts along the line will be upgraded to make them suitable for electrification. Credit: Network Rail.
The electrification between Leicester, Derby/Nottingham and Sheffield is scheduled to be completed by December 2023. Credit: Network Rail.

Midland Main Line (MML) runs between London St Pancras and Sheffield, bypassing Luton, Bedford, Corby, Leicester, East Midlands Parkway, Derby, Nottingham and Chesterfield in the UK.

Network Rail and the UK Department for Transport initiated MML’s improvement in 2014, which includes electrification of the line, upgrading bridges and tunnels, remodelling the stations and line speed enhancements.

As part of the £1.5bn ($2bn) MML improvement programme, a section the line between north of Bedford to Kettering and Corby was electrified in November 2019. The electrification of another section of the MML located north of Kettering to Leicester, Derby/Nottingham and Sheffield is scheduled to be completed by 2023.

Midland Main Line (MML) improvement project details

Opened in 1870, the Midland Main Line (MML) has 397 miles (639km) of track, 16 tunnels and 35 stations. Network Rail initiated the MML improvement programme with an objective to increase the passenger capacity, reduce the journey times, and curtail the carbon footprint up to 11,000t by introducing greener trains through electrification.

The project includes electrification of 639km single track, erection of 12,500 overhead line equipment (OLE), establishing four national grid supply points, and 24 substations or distribution points along the line. The project also includes modernisation of track and signalling systems, expansion of station platforms and introduction of new trains with more carriages.

The line will be electrified using a 25kV OLE design, including wires and supporting posts that will distribute electricity at 25,000V to power trains.

As part of the electrification of the Midland Main Line from Bedford to Corby, 13 bridge reconstructions were undertaken to enable clearances for Overhead Line Electrification (OLE).


Network Rail began initial works of upgrading the tracks, which are necessary for instigating the electrification works, in 2014. The upgrades to the line include performing enhancement works to bridge parapets, strengthening railway embankments, and clearing the overgrown vegetation.

Construction on the line for electrification includes undertaking piling works to install the foundations for structures that will carry overhead lines, and installation of overhead line equipment.

The piling works between Kettering and Corby began in Kettering area in June 2015. The works are aimed at widening and strengthening the railway embankment to facilitate the existing line to be realigned and a second line to be installed.

The line between Kettering and Corby was closed for train operations between September and October 2016 to strengthen and carry out upgrade work on key bridges and viaducts along the route.

The construction of a new facility with four rail sidings near the Kettering railway station was finished in November 2020. It included 1,425m of new plain line track which complements the MML’s electrification by supplying the new electric trains with a stabling facility.

Trains will run between London and Corby from May 2021. One additional train will run every hour between Corby and London until the project is finished.

In December 2020, the teams removed more than 300 equipment units that were no longer needed from the tracks between Wellingborough and Kettering and the building next to the overhead line.

Upgrade work included 23km new track for the fourth line, 1.5km of embankment works, the reinforcement of 15 structures and the installation of 105 new signals and 11 new gantries.

The new line adds space to the route, allowing longer trains with more seats between Corby, Kettering and London St Pancras, and will have capacity for six trains per hour to London St Pancras.

The electrification of the line from Leicester, Derby, Nottingham and Sheffield is expected to be completed by December 2023.

Contractors involved with the MML improvement

Atkins was awarded a contract to update the business case for MML electrification in 2014. The contractual scope included performing route enhancements, cost evaluation and rolling stock assessment. The company is also providing engineering design services for the electrification of the line.

Carillion and SPL Powerlines joint venture was awarded a €450m ($750.95m) contract for the electrification of the MML in February 2014.