By 1990, electrification had reached , and in 1991 Edinburgh Waverley. The Mark 3B range was used throughout the electrification scheme, certain areas are presently being upgraded to the Mark 3D design range, this will eliminate known corrosion issues with the AWAC catenary and replace solid stainless steel droppers with flexible copper current carrying designs. Some headspan to portal conversions are also taking place. In order to keep construction teams working, two additional schemes were authorised, to and (North Berwick Line). At the peak of the electrification project during the late 1980s, it was claimed to be the "longest construction site in the world" at over . West Anglia / Fen Line This covers the lines from (Bethnal Green Junction) to , , and . In the 1960s, the lines to Chingford, Enfield Town and Cheshunt were electrified at 6.25kV, from Cheshunt to and Hertford East at 25kV. The Lea Valley line between Coppermill Junction and Cheshunt was electrified at 25kV in 1969. All the 6.25kV areas were converted to 25kV in 1983. In 1987, electrification was extended from Bishop's Stortford to Cambridge at 25kV. In 1990 the line to opened, and in 1992 electrification was extended from Cambridge to along the Fen Line. Great Eastern Main Line London Liverpool Street to Norwich. Converted from 1,500 V DC (see 1,500 V DC section "Shenfield Metro") Converted from 6.25 kV/1,500 V DC to a combination of AT and FT 25 kV Mark GE (Great Eastern) between 1976 and 1980. Presently being upgraded to the GEFF (Great Eastern Furrer + Frey) range altering the catenary from a compound to simple sagged arrangement. Romford–Upminster line Shenfield–Southend line Crouch Valley line Braintree branch line Mayflower line Sunshine Coast Line London, Tilbury and Southend line to . The majority was originally electrified at 6.25 kV, final sections converted to 25 kV in March 1989. London Overground Local lines within London electrified with 25 kV are: North London line, between and . Lea Valley lines Gospel Oak to Barking line Various other suburban lines in the north of the city are electrified as part of other routes mentioned above. West Midlands West Coast Main Line routes electrified in the 1960s: Trent Valley line Stone to Colwich Line Rugby–Birmingham–Stafford line Stafford–Manchester line Walsall–Wolverhampton line Commuter lines out of : Cross-City Line: electrified 1993 Chase Line: New Street to completed 2017 Manchester and North West area Manchester to