Network Rail has shared images showing its progress so far on the Watford Junction to London Euston upgrade work.
The Bakerloo line and London Overground have been closed for improvements to be made between July 23 and August 25.
With the second week of work complete, 6,000 railway sleepers have been replaced, 1.5km of cables have been installed, and plants and trees near overhead lines have been cut back, between Euston and Watford.
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The new cabling aims to make the signalling system more reliable so passengers should see fewer delays, according to Network Rail. Wooden sleepers are also being replaced with new concrete sleepers.
Platforms at three overground stations have been resurfaced with six, including Watford High Street, set for improvements in total.
Overall, Network Rail will be installing 48km of cabling and replacing 18,000 railway sleepers.
The work is divided into four phases, phases 1 and 2 are already complete and work on phase three is set to end on August 17.
In the current phase, the Bakerloo line is closed from Queen’s Park to Harrow and Wealdstone while the London Overground is closed from Euston to Watford Junction.
During phase 4, the Bakerloo line will be fully open while the London Overground will remain closed between Willesden Junction and Watford Junction.
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