i was thinking about a railroad overpass on a busy road in my area (manville, nj) and how at one time it may have been at road level similar to another in the same area. If this were true, the road was lowered and the track raised, and i’m wondering by how much. If it were raised, the grade on either side of the bridge may have been relatively high. a “hump” which shouldn’t really affect the locomotive since the whole train wouldn’t be going up the grade at the same time, once the loco was past the grade changes, there’d be just as many cars going up as down the grade.
Normally the railroad wouldn’t raise it’s track and roadbed for the overpass unless there was some special situation. The road would be lowered (dug in) the necessary amount and graded for a smooth transition for road traffic.
To model it, just add a second layer of roadbed material. Cork or WS foam. But you will have to watch how much of a hump you wind up with or the RR cars will uncouple when going over it.
i think if you look closely you will find that the highways usually change elevation to get under the tracks. in other words, don’t raise the bridge. lower the river. exceptions would be in major metro areas where years ago the railroads elevated their track structure to eliminate all crossings at grade level for many miles through the city.
What you’re describing is EXACTLY what the Western Maryland and PRR did in Hagerstown, Maryland in the 1950’s. This map gives a pretty clear picture of what was done.
The original WM alignment followed what is now Burhans Blvd., and the PRR (Cumberland Valley) followed Walnut Street. Both were at grade, and the WM was particularly busy, being the east end of the Hagerstown Yard complex, as well as the passenger station for the city. (You can still see the station, the long building between Washington and Franklin streets). The re-grading of the lines began a good ways “down stream”, with the WM’s yard tracks being part of the new grade. The PRR grade was shifted west, and gained elevation to join the grade used by the WM. Originally, the PRR maintained a separate track to North Junction, where it crossed the WM on its way to Shippensburg. Today, Norfolk Southern operates the PRR line, and CSX has the WM. Instead of crossing the lines at a diamond, the lines join a short distance south of North Jct., then diverge again at a switch at the junction.
It appears that the roadways were excavated out to some degree, but the railroad was definitely moved to higher ground, as evidenced by the new position of the right of way in
Since the premise isn’t realistic, you wouldn’t raise the railroad to clear a road, there is no way to do it “realistically”.
One railroad might rise up over another while another goes down, but it isn’t that common. The grades are only going to be a percent or so. Assume 30 ft clearance rail to rail, That is about 3000 ft plus vertical curves on each side. So that would be about a 30+ run of grade on each end.
Another location where this occurs is in Baltimore, where a combination of a road going down and a railroad going up creates the situation at the B&O (CSX) crossing of Boston Street.
The Norfolk Southern (formerly CR, PC and PRR) is on the left in the map image, and crosses at grade, while the B&O rises up a bit to cross on a bridge.
As a general rule, the railroad’s profile is fixed, and the road has to be dug down (or elevated) to the suitable level for clearances. One exception is the already noted one where there is a major program through an urban area to separate a whole series of road/rail crossings. Then the cost of raising or lowering the tracks can be offset by multiple savings in the road portion. Was there not a recent example of this in Nevada, either Las Vegas or Reno?
The other time where the rail profile might get tweaked is the case where it is already in a sag at the road crossing. Raising the rails 2-3 feet, maybe as much as 5 feet, might not require an unmanageable distance to run the lift out.
The idea of a “hump” since only a few cars will be on it at any given time is not in practice workable. In a long heavy freight train it is a situation almost guaranteed to break knuckles. Quite doable for light rail transit equipment, but they are short with every car powered, so the train forces are very different.