This paper was written by Tom Corker, the IRSE Thorrowgood Scholar for 2016, and was published in IRSE NEWS April 2017. The national railway network in Japan is operated by six vertically integrated regional companies, who own and operate the infrastructure and passenger trains.

Freight trains are operated nationally by a separate operator, JR Freight, on the infrastructure owned by the other six companies.

These companies were formed from the privatisation of Japan National Railways in 1987, and now make up the JR Group. The national network is supplemented by substantial networks of private lines, mainly commuter operations in urban areas. The national network is comprised of two distinct systems. Conventional lines are narrow gauge (1067 mm) and make up the majority of the network in terms of route miles, with top speeds of 130-160 km/h. The high-speed passenger only Shinkansen system is standard gauge (1435 mm) and therefore isolated from conventional lines.

Conventional lines use what could be described as a hybrid system of route and speed signalling, reflecting the mixture of historical British and North American influences. Main signal aspects carry speed information, but the driver is also provided with specific routing information via multiple signal heads or route indicators.

ATC (automatic train control) systems have been in use on Shinkansen lines ever since their inception. The original system installed on the Tokaido Shinkansen in 1964 used modulated audio frequency track circuits to transmit speed codes to trains, which were capable of automatic braking from one speed code level to the next. However, this tends to result in a stepped braking profile, which limits capacity and reduces ride comfort. These speed code based ATC systems have now largely been replaced with digital ATC systems. Digital messages containing stopping point information are transmitted via track circuits. The onboard computer stores the route information, including speed limits, gradients and track circuit identities, which are used in conjunction with a tachometer to determine the train’s position. Automatic braking is along a smooth profile, overcoming the problems associated with the older analogue system.