Tightlock coupling
Type H Tightlock is a North American version of the Janney coupler used on passenger trains. It smooths running by reducing slack and helps prevent telescoping in crashes, while still working with other Janney couplers used by freight railways.
Like other Janney couplers, Tightlock is semi-automatic: cars lock together automatically when pushed, but a worker must go between cars to connect air brakes and power/electrical cables. To separate, a lever must be used to release the locking pin.
In Europe, some operators tried making Tightlock fully automatic by adding pneumatic and electric connectors, but these were unreliable, so most switched to the fully automatic Scharfenberg coupler.
Standards for Type H Tightlock were set by the Association of American Railroads and later handed to the American Public Transportation Association in 1971 when passenger service was nationalized in the United States.
On standard-gauge rails, the coupler height (measured from rail top to coupler center) is about 33 inches. The allowable height is 34 1/2 inches maximum for empty cars and 31 1/2 inches minimum for loaded cars, with small tolerances.
AAR Type F Vertical InterLock couplers are a different kind often used on gondola wagons that go through rotary dumpers.
In the UK, Tightlock was widely used on multiple-unit trains built from the mid-1970s. Earlier slam-door units with Buckeye/Henricot couplers required a shunter to trip the mechanism and connect air and electrical leads. To save staffing costs and reduce station dwell times, British Rail adopted automatic Tightlock systems on new power-door trains, starting with the Class 313. This included air-operated Tightlock and underslung electrical connectors controlled by a drum switch, allowing drivers to couple or split trains from the cab.
Tightlock had some success in the UK but also reliability issues and wear from constant coupling and uncoupling. The Connex South Eastern Networker fleet faced notable problems, and procedures were updated to ensure the knuckles were fully engaged. By the early 2000s, Bombardier Electrostar Class 375s were built with Tightlock for some services, but Dellner couplings were preferred, and later units used them (with earlier Tightlock units modified).
Today, all newer UK multiple-unit trains use Dellner couplings.
This page was last edited on 2 February 2026, at 17:17 (CET).