The following is taken from Congressional testimony of Matt Rose (CEO of BNSF):
"At sustained speeds in excess of 90 mph, passenger train operations will need to be segregated from freight operations on separate track. The level of maintenance work required, the very different impacts passenger and freight rolling stock have on the surface of the rail and managing the flow of train traffic with such differences in speeds would make the joint use of track uneconomic and impracticable.”
I understand his point about about speed differential being a problem. However, the portion that refers to “different impacts of passenger and freight rolling stock on the surface of the rail” leaves me puzzled. I would have thought that any stretch of rail that is built for really heavy duty freight – say the joint line out of the Power River coal fields – would need nearly nothing done to the rail and roadbed to accomodate high speed rail.
Obviously, I am wrong, but could someone explain what track structure improvements would be required?
Just a thought…Maybe the elevation of the outside rail on curves for very high speed of passenger operation is a different requirement than for a heavy freight operation at lower speeds…and I wonder about harmonic forces transferred to the track from the two different types of train operations…weight vers. speed.
I’m not an expert on rail impacts and won’t comment on that, but one of the biggest concerns in track structure between freight and high speed passenger is “cant,” or superelevation on curves. In order to increase train speed on curves for fast passenger operation, the outer rail has to be raised higher than what is needed for the lower speed freight trains. This extra cant could induce stringlining on long, heavy freights…IE…cars pulling off the track on the inside of the curve. For this reason, high speed passenger and freight are not compatable where any amount of medium to sharp track curvature is involved.
I will give Donner Pass as an example. The line is steep and very crooked, with freights generally limited to 25 MPH and the CZ to 30. Increasing the cant to allow the CZ to speed up would jeopardise freights in that they would have to shortened and lightened in order to keep them from derailing. Tilt trains would be better using the existing track structure, as they can take curves much faster than the current high level equipment. However, increasing the cant sufficiently for very fast passenger trains would take an entirely different alighnment…much, much straighter and with a very high cant. But this would shorten the distance across the pass and increase the grade, and this combined with the high cant would prohibit freight trains entrirely.
These differences in dynamics and forces between a freight train and a passenger train have been disussed many times here and in rail publications like Trains. Basically speed and weight are the variables which cause different forces on the rail. Higher and longer freight cars are different from passenger cars and from old 40 or 50 foot box cars, thus track dynamics are different. And of course, the higher the speed of anything the more critical the specifications of a track are set and maintained; theoretically there is no leeway. And when we talk track we are not just talking rail and ties but also the ballast and whole substructure from the ground to railhead. I am not an engineer and I doubt I could understand much beyond what I have said. But there are magazine articles and whole books on the subject which would clarify the differences in minute detail.
What he’s saying is that the heavier impacts of freight will damage the track more than passenger and so require more maintenance The tighter tolerances required for 90 mph will degrade faster under heavy freight and require more maintenance, which ends up delaying things more.
Stepping up from class 4 to class 5 track significantly decreases the permissible deviation in the track. A the track is allowed to have a deviation in line of 1 1/2 inches at class 4 and is only allowed 3/4 in at class 5. There are similar differences between surface and crosslevel at the different classes of track.
Diesel Power is good for about 110mph max, above that Electric power or Turbine would be neeeded.
The 6 car Acela reaches 150mph but requires 12,000 hp.
ATC track control and Cab Signals would need to be installed.
A derailment at 30mph, a lot of coal spilled on the ground. A passenger train derailment at 150mph, large loss of life. Inspect Track each day.
Four Quadrant Gates at all Grade Crossings
You dispatch that Freight Train, in 30 minutes it’s 15 miles out. Then you dispatch a Bullet Train at 150mph. It’s closing on the Freight at 2 miles a minute. Less than 10 minutes later you have impact (or the Bullet Train has slowed to 30mph).
Think of this, you dispatch a 60 car Freight Train for a track speed of 30mph. The 100 ton hoppers are pounding the rails and curves at slow speed. Then the Bullet Traine comes along, almost flying on the top of the rail, any rail problem is a big problem. In the NE Corridor Track Inspection Cars run from Washington to Boston at night, then back the next night.
In the Northeast Corridor an Acela Bullet Train goes out every hour, track speed 135 to 150mph. Local Freight Service is in the middle of the night. Through Freight Service from the Washington area to the Boston area is by CSX or NS on there own tracks or trackage rights over Regional Lines. Rhode Island has even added a third track from Providence to the Kingston Industrial area just to keep freight off the Corridor.
Mr. Rose is absolutely correct. Mixing heavy freight trains and high-speed passenger trains on the same track will create high track maintenance costs, result in schedule unreliability for passenger trains, cost a significant capacity loss for freight, offer poor ride quality for passenger, and in the end will cost more than separate infrastructures. This is nothing new – the principles were understood more than a century ago – but science and fact is seldom an obstacle to people blessed with a little bit of knowledge and a whole lot of self-impression.
Track geometry for high-speeds must be maintained to much higher tolerances for cross-level, runout, and gauge. The cost of this is extremely high. The rate at which track geometry migrates out-of-tolerance is proportional to the maximum axle loading and the gross tonna
Double RED at a Draw Bridge