Wednesday, February 23, 2005
By Jim CameronSpecial to WestportNow
Metro-Norths mangled and much-maligned service in Connecticut is made all the more challenging by a technological quirk of fate. Ours is the only commuter railroad in the United States that operates on three modes of power—AC, DC and diesel.
On a typical run from, say, New Haven to Grand Central, the first part of the journey is done ғunder the wire, the trains being powered by 13,000-volt AC overhead wires, or catenaries.
Around Pelham, in Westchester County, the conversion is made to 660-volt DC third rail power for the rest of the trip into New York. Even diesel trains must convert to third-rail as their smoky exhaust is banned in the Park Avenue tunnels.
And thereԒs the rub: Connecticut trains need both AC and DC, overhead and third-rail, power pick-ups and processors. That means a lot more electronics, and added cost, for each car. While the DC-only new M7 cars running in Westchester cost about $2 million each, the proposed dual-mode M8 car designed for Connecticut could cost $3.5 million each.
So, some folks are asking Why not just use one power source? Just replace the overhead wires with third-rail and we can buy cheaper cars.Ӕ Simple, yes. Smart, no. And heres why.
ThereҒs not enough space to lay a third-rail along each of the four sets of tracks in the existing right of way. All four existing tracks would have to be ripped out and the space between them widened. Every bridge and tunnel would have to be widened, platforms moved and land acquired. Cost? Probably hundreds of millions of dollars, years of construction and service disruptions.
Even with third-rail the Connecticut Department of Transportation (CDOT) would still be required to provide overhead power lines for Amtrak. That would mean maintaining two power systems at double the cost. Were currently spending billions just to upgrade the eighty-year old catenary, so why then replace it?
Third-rail AC power requires substations every few miles, meaning further construction and real estate. The environmental lawsuits alone would kill this idea.
DC-driven third rail is less efficient. Trains accelerate much faster using overhead AC voltage, the power source used by the fastest trains in the world—the TGV, Shinkansen, etc. On third-rail speeds, are limited to 75 miles an hour vs. 90 mph under the wire. That means, mile for mile, commute time is longer using third rail.
Third rail ices-up in bad weather and can get buried in snow causing short circuits. Overhead wires have problems sometimes, but they are never buried in a blizzard.
Third-rail is dangerous to pedestrians and track workers. The idea of conversion to third-rail was studied in the 1980Ғs by consultants to CDOT. They concluded that, while cumbersome and costly, the current dual-power system is, in the long run, cheaper and more efficient than installing third-rail. This time, the engineers at CDOT got it right.
Not satisfied, some of the third-rail fans are now pushing bills through the legislature to study the replacement scheme yet again. More studies would mean years of delay in ordering already overdue car replacements.
I trust the legislature will dispense with these nuisance proposals quickly and get on with the task at hand—ordering new cars now. Even if the needed funds are appropriated today and the order placed immediately, new cars wont be delivered for five or six years. Further studies of third-rail vs. overhead catenary only make us wait longer.
Posted 02/23/05 at 03:06 AM Permalink
CommentsYou must have a Facebook account and be logged to this account (login/logout button above) to post comments. Comments are subject to our Comment Policy.
If the powers that be were willing and able to think in the really long term, the obvious solution would be to convert all Metro North trackage to AC overhead current. This would of course have to include not only the New Haven, but also the Harlem and Hudson Divisions. I recognize the problem of clearance in the Park Avenue Tunnels. Environmentally, there is no room for Diesel power in urbanized areas. It should be eliminated. Come on guys, think creatively. If the Euros can do it, why not us ?
After all, Thomas Edison was an American !!
A portion of the “third-rail” system going into Grand Central has (or did have) short stretches of overhead contacts to bridge gaps in the third rail, and the old NYC&HR electic locomotives had a very small pantograph to make contact. Seems to me that there is adequate room in those tunnels to provide an overhead electrical system and eliminate the third rail altogether. The overhead wire can be single-suspension supported on insulated clamps without the space requirement and expense of the compound catenary used in open construction, because the trains are running slower in the tunnels and plenty of stiffness can be obtained with more frequent clamps to retain the overhead line.
I guess one would have to be more familiar with the clearances involved than I am to say for sure, but it would seem reasonable to examine.
Tom Fairbairn—Minneapolis, MN