Claim: The four-rail Railway electrification system was unable to solve the issue of Victorian systems, which were not constructed to carry currents, and had no way to keep stray earth currents at a reasonable level.
Evidence: Some of these, particularly Victorian mains that predated London's underground railways, were not constructed to carry currents and had no adequate electrical bonding between pipe segments. The four-rail system solves the problem. Although the supply has an artificially created earth point, this connection is derived by using resistors which ensures that stray earth currents are kept to manageable levels.