In article ,
Richard J. wrote:
Even if running in tunnels is considered dangerous (despite it being
regarded as perfectly safe without radios for a century or so),

When they didn't have radios, they had a guard. It was the move to OPO
that - I think - drove the desire to have good comms between motorman
and signaller.

--
Shenanigans! Shenanigans! Best of 3!
-- Flash