This is extremely interesting, and I looked further into the Wikipedia link in Guest Nathaniel's previous post, and want to birng attention to this paragraph on there about the United NJRR and Canal Company:
"In November 1832 the NJRR acquired control of the
Newark Turnpike, which paralleled the planned alignment east of
Newark, to avoid problems caused by competition. The stock of the
Essex and Middlesex Turnpike, running south from Newark to New Brunswick, was bought April 6, 1833; the majority of the line was built directly along the
turnpike. The alignment as originally planned crossed the
Passaic River on the
Centre Street Bridge, then curved south along
Park Place and
Broad Street directly into the turnpike. A branch would have run from the west end of the bridge south along the river and then southwest to the main line at the south end of Broad Street, but this became the main line and the original plan along Broad Street was never built."
So, in playing a little Sherlock here, I checked out 'Essex and Middlesex Turnpike', which lo and behold, makes up most of what is today's Route 27 in New Jersey, which in turn runs only a few feet away from the Northeast Corridor tracks for a good portion, especially just south of Rahway and thru Metropark. In this stretch, trains and autos race each other and people from one vehicle transport either wave or look at each other. Route 27 intersects the Corridor near Newark and at New Brunswick. Although it has straight, tangent sections, there are places where it gets curvy.
So this lead to a tantalizing question: is today's S-curve simply a holdover from the way the turnpikes were oriented? Meaning, that the Essex and Middlesex's stock was bought by the young United NJRR and CC to more or less follow it's alignment with as little interference as possible. We MAY have our answer, in yes. Looking at today's street grid in Elizabeth NJ, many roads there bend and even break continuity, right near that stream I was talking about that goes under the tracks, named appropriately the Elizabeth River, a tributary of the Arthur Kill waterway that separates New Jersey from Staten Island, NYCity. The streets, and even that long abandoned Jersey Central main that ran into the Pennsylvania mountains, all curve in this part of town. Likely, the deeds to build turnpikes were influenced by natural barriers, like waterways, and since we were talking horse and buggy thoroughfares, straight measurements were easy through the forests and woods, but get to a waterway and suddenly things start bunching up.
That the Northest Corridor was germinated in this part of New Jersey by a fledling railroad who guided itself on dirt roads and horse and buggy turnpikes, combined with the presence of a waterway, may finally settle how our S - curve came to be.
The decision to leave it alone or seriously tame it, for me I'll continue tomorrow.
This little excercise was fun and hope the discussion doesn't end!