Thursday, August 19, 2004


Choo Choo Charlie Was An Engineer

Continuing yesterday's missive on transport, perhaps the biggest problem facing regions is the obsolescence of facilities. The Tappan Zee Bridge for example, was designed for a useful life of only 50 years, which is just about up. The locals, well remembering the machinations that got the bridge built originally, or out of just plain NIMBYism are dead-set against any replacement project. Something must be done because the bridge is now constantly under repair, and well over capacity (despite three lanes in each direction plus a reversible lane). Some of the traffic issues on the bridge may be traced to the original poor design of the I-287 / I-87 interchange in Elmsford about 2 miles south of the toll plaza, where the original assumption was that traffic would predominantly flow south toward New York City. The planners didn't consider the explosive growth of corporate campuses in the White Plains corridor, and the traffic matrix shows that a lot of the commuters into that corridor are coming from Rockland and north Jersey. The traffic jams extend all the way across the bridge, and frequently as far back as Route 303 in the morning rush (sun glare and the eastbound toll don't help). While the interchange is being reconstructed to reflect current realities, it doesn't resolve the bridge problems.

Caro's book on Robert Moses criticized him for not including support for heavy rail (read as rapid transit as opposed to mainline rail) on several major bridges in the NY metro area. The idea of rails across bridge infrastructure generated much political give and take going as far back as the Brooklyn Bridge, where the running gag was that the trackage originally installed on the bridge was put there for the convenience of Brooklyn politicians wanting to get up to Saratoga for the weekend. The Brooklyn Bridge's trackage was removed during its late 1940s upgrade supervised by David Steinman, reflecting realignment in the subway infrastructure as much as gaining additional traffic lanes on the bridge. Subway trackage was removed from the Queensborough Bridge when the Second Avenue elevated line was demolished (the original plans for the bridge had four subway tracks crossing, however, the designing and consulting engineers found some errors in the load calculations before the bridge opened, and had two tracks removed and diverted to the tunnel which feeds the Astoria line). Obviously, the Williamsburgh and Manhattan Bridges both still have their heavy rail trackage, but both of those bridges have been under constant repair for decades, in the Manhattan Bridge's case in large part due to torsion effects from the trains passing over (the IND tracks on the north side of the bridge were much more heavily used than the BMT tracks on the south side, causing lengthening of the suspenders). Interestingly, all four bridges had light rail (trolley) tracks, which rather nicely provided service from all parts of Brooklyn and Queens (even those rather underserved by subway service) into Manhattan. Of course, New York City abandoned light rail altogether in 1950 (although there is the occasional squawk about putting in light rail on major Manhattan cross-streets like 42nd).

Of course, there were plenty of other light rail systems that were eliminated around then, apocryphally with a bit of help from certain bus makers. The famed examples include the Pacific Electric system in Los Angeles, and the Key System in the San Francisco area (the Key system was an effective feeder for the East Bay area into downtown SF, via the Bay Bridge; the bridge originally had traffic flowing in both directions on each level of the bridge, additional traffic load required changing the configuration to dedicating each level to a single direction, and to maintain capacity, the tracks had to go). Interestingly enough, the Bay Bridge and the Benjamin Franklin Bridge in Philly are the only other modern examples of rails on suspension bridges in the US (the original Roebling bridge at Niagra Falls did have railroad tracks on its upper level, however, this bridge has long since been demolished). The generally accepted wisdom up until fairly recently was that heavy rail was in general not a good thing for suspension bridges, due to flexibility and torsion issues, as well as load issues associated with freight (since in the US, there were no mainline railroads using suspension bridges, this was pretty much a moot point). However, worldwide, there have recently been several new major suspension bridges kitted out with heavy rail, such as the Tsing Ma in Hong Kong, the Inland Sea in Japan, and the Tagus (I really know it as the Salazar Bridge, but I guess it's not PC to mention him these days) in Portugal has actually been retrofitted with trackage. However, a couple of major new bridges had trackage nixed - the Akashi (Japan) and Great Belt (Denmark).

Which brings us back to the Tappan Zee Bridge, as sooner or later the bridge is going to replaced or upgraded. There is a huge regional planning push for trackage on the replacement, which makes sense in a number of ways. First, a well planned connection from the Metro North and New Jersey Transit lines on the west side of the river to a reasonable cross-Westchester line (with adequate stops along the I-287 corridor to enable feeding the campuses) could substantially reduce the commute traffic, and potentially enable a one-seat ride into Manhattan from Rockland if planned properly (an additional track is being added to the Harlem line, and there are four tracks on the Hudson line; the alignments would be tough, but doable given the resolve to do something). Thinking even further out, a rail corridor along I-287 could conceivably feed into the New Haven line near Port Chester, with the concomitant easing of traffic to and from Connecticut; it would also potentially greatly help out on those all-too-frequent occasions when something goes wrong on the New Haven line between Woodlawn and Harrison and no trains get out for hours).

More to come......


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