Can High Speed Trainset units be coupled together when moved dead in tow?

• A. No, HST units must not be coupled together.
• B. Yes, they may be coupled together.
• C. Yes, if pantographs are down only.
• D. Yes, if the power is off.

Answer: (A)

High-speed trainsets rely on a powered lead unit to coordinate braking, traction, and all electrical and pneumatic interconnections across the set. When a unit is moved dead in tow, there is no active control from a lead power source, so the control circuits, brake piping, and safety interlocks for the trailing unit cannot be guaranteed to function correctly. Coupling another HST to a dead unit would bring together two units without the necessary powered control, increasing the risk of improper braking, accidental movement, or damage to couplers, hoses, and electrical connections. Because these safety and control links aren’t active in dead-in-tow conditions, the prudent and safe practice is not to couple HST units together.