 Status of new signal systems?
I understand the NYCTA is experimenting with new signal
technology that is more efficient. It uses a 'rolling block'
technique so that the zone of protection moves with the train
rather than by fixed wayside signals. Also, it saves the
expense of wayside signal installations, relay logic, and
cabling.
I thought prototype experiments would be conducted on either
the L or 7 lines because those lines are not shared with other
routes. For experiments such as this, both the wayside and
rolling stock are modified.
Would anyone know the status of these experiments? If they've
been hooked up, how well has the new approach worked in
actual service conditions?
FWIW, SEPTA is replacing the 1950s signal light system on
the Mkt-Fkd line (which in turn replaced semaphones from 1907),
but is still a fixed block system, only with fancy cab signals.
A similar system is going in the subway surface lines, and
also went in on the P&W. The Broad Street Subway still uses
the basic signal light system from 1928 (some extensions
use new equipment), plus Identra from the late 1950s.
When I visit NYC subways, it amazes me how close the signals
are, and how much it must cost them to maintain them all.
The logic is complex since obviously with close signals
multiple blocks behind a train have to go red for safe
stopping.
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