The Manchester–Sheffield–Wath electrification project was finally completed in 1955, using overhead wires energised at 1,500 volts DC. Whilst this was tried and tested technology (and is still standard in the Netherlands), the comparatively low voltage meant that a large number of electricity substations and heavy cabling would be required. It also made regenerative braking by transfer of power from descending to ascending trains in the same section of line comparatively straightforward. The main contractor for the electrification work was Bruce Peebles & Co. Ltd., Edinburgh. Following technological developments, especially in France, 1.5 kV DC was soon superseded by the later network standard of 25 kV AC. This left the Woodhead line as the only main line in the UK with 1.5 kV DC electrification.