Railway electrification in Great Britain began during the late 19th century. A range of voltages has been used, employing both overhead lines and conductor rails; the two most common systems are 25 kV AC using overhead lines and the 750 V DC third rail system in southeast England and on Merseyrail. In 2006, 40%— of the British rail network was electrified, and 60% of all rail journeys were by electric traction (both by locomotives and multiple units). According to Network Rail, 64% of the electrified network uses the 25 kV AC overhead system, and 36% uses the 660/750 V DC third-rail system.