Hardly
a season goes by without service on Metro-North being disrupted by a “wires
down” accident. That’s when the overhead
catenary
that powers our trains breaks or is ripped from its poles, cutting electricity
and service and ruining the commute for thousands.
But
why do we rely on such fragile wires, some of them installed 100 years
ago? Isn’t there a better way of
powering our trains? Probably not.
Consider
this: ours is the only commuter railroad
in the US that relies on three modes of power:
AC, DC and diesel.
Trains
leaving Grand Central first operate on 750
DC current picked up from the third-rail,
just like NYC’s subways. Around Pelham,
in Westchester County, the trains raise their pantographs (those triangular
shaped contraptions atop the cars) and convert to 12,500 volt AC current picked
up from the catenary, hence the phrase “operating under the wire”.
On
the Danbury and Waterbury branch lines there is no electricity, so those trains
must be powered by diesel. But even those
diesels must operate on third-rail power in the Park Avenue tunnels for
environmental and safety reasons.
That’s
a lot of technology for one railroad to administer, and a lot of
electronics. That is why the M8 cars
that operate on AC and DC require separate power processing, adding to their
cost. The third-rail only M7 cars that
run on the Hudson and Harlem lines cost about $2 million each. But our newer and more complicated M8’s cost
about $2.75 million apiece.
So
a lot of people ask me… “Why not just use one power source by converting the
entire line to third rail?” As with so
many other seemingly simple solutions there are several good reasons why it
wouldn’t work.
Mind
you, the idea was studied by CDOT in the 1980s and rejected. And here’s why:
1) There’s not enough
room to add a third rail along most of the four-track system. You’d have to move the tracks, widen the
right-of-way and expand a lot of the bridges and tunnels it uses. Imagine the cost.
2) Even if we did convert to third-rail, we’d still have to
maintain the overhead catenary system for Amtrak whose locomotives get their
power under the wire.
3) A third-rail power system needs more real estate: power substations every few miles, adding to
construction and cost.
4) Third-rail DC power is nowhere near as efficient as
overhead wire AC power. That means
slower acceleration in third-rail territory and speed limits of about 75 mph vs
90 mph under the wire. Remember… the
fastest trains in the world (like the TGV and Shinkansen) operate under the wire,
though theirs is not as aged and brittle as ours.
5) Third-rail is dangerous to track workers and
trespassers. Overhead wires, much less
so.
6) Third-rail can ice up and get buried in blizzards,
causing short-circuits. We’ve had some
amazing winter weather in Connecticut, but nothing that piled snow high enough
to touch the overhead wires.
I’ll
admit that weather does cause problems for the catenary. In extreme heat it can expand and sag and in
bitter cold it can become brittle and snap.
Both conditions require our trains to operate (even) more slowly, but
they still get you where you’re going.
So
what’s the solution to our “wires down” problems? Accelerated replacement of old wire, better
maintenance of pantographs and a little common sense… and not conversion to
third-rail.
Reposted with permission of Hearst CT Media