Published at 12:12 on 2 December 2020
Stories like this one are circulating in the local news.
What we actually have here is the nexus of several factors:
- A prosecutor trying to make those whom s/he is accusing look as bad as possible (as prosecutors always do),
- A reporter ignorant of the basics of railroad signaling and railroad operations in general,
- Broadly-worded post-9/11 anti-terrorism legislation, and
- A couple of activists who badly neglected their homework.
What we do not have is a gang of hardened and depraved eco-terrorists willing to cause significant human and ecological damage in order to make their point.
First, we need to look into just what the “shunting” these two are accused of actually does. In order to do that, we must delve a bit into the basics of railroad signaling.
The Basics of Railroad Signaling
There is much talk these days about “smart” vehicles and “smart” highways, and how these offer the possibility of vastly safer road transport in the future. Well, railroads have been creatively using late nineteenth-century technology to minimize the likelihood of crashes basically ever since… the late nineteenth century! It’s one of the reasons rail is such a safe transport mode, compared to highways.
What they do is called automatic block signaling. The railroad track is divided up into a series of electrically-isolated blocks and small opposing electrical charges, typically around a volt or so total, are applied to the two rails in each block. Even though the rails are not very well-insulated from either the ground or each other, the small voltage means that very little current will flow between them.
That is, unless a train is present. Then, a current will flow up through one steel wheel, across the steel axle, and down through the other wheel, completing the circuit. This current will trigger a relay. The presence of a train has been detected.
It is then a simple enough matter to use electromechanical logic to cause signals to turn red, disallowing two trains from occupying the same block at the same time. If one successfully does that, crashes between trains become impossible.
The same principle can be used to activate signals at grade crossings. (Although, to be technical, what is now done at crossings is rather more sophisticated, allowing the distance and speed of the approaching train, as well as its mere presence, to be detected.)
These days, most signals have been upgraded to computerized and electronic controls more sophisticated than the old electromechanical ones, but the basic principles remain the same: voltage is applied to the rails, and when current can easily flow between the rails, it is interpreted as the presence of the train and signals are set accordingly.
If you wish to see a diagram of how this all works, go here.
The Basics of Shunting
Of course, if one were to connect a sufficiently thick wire between the two rails, and electrically bond the wire to the rails with low-resistance connections, one would create a short between the rails that mimics the presence of a train. This is all that shunting does, no more, no less.
Remember how I mentioned that the two rails are not well-insulated from each other? Well, it turns out that sometimes moisture or metallic debris can cause an accidental and unwanted electrical connection between the rails.
Either way, we now have a phantom train on the block. The signaling system thinks a train is present, even though none is. Railroad operations are being disrupted.
This happens frequently enough that railroads have a procedure for dealing with it. After the train stops, the dispatcher can tell the engineer to proceed through the red light. The catch is that the train has to proceed very slowly, slow enough so that, if there is something on the tracks, the train can be stopped before it hits it.
The real solution, of course, also involves dispatching a repair crew to locate and cure the root cause of the problem. Making trains stop, contact the dispatcher, and creep through a block needlessly slowly still costs time and money.
What Shunting Can, and Can Not, Do
Now that we know the basics of what the two have been accused of, and how railroads operate, we can delve into some of the supposed adverse consequences of the alleged crimes.
Shunting Will Interfere with Railroad Operations
How could it not? It causes signals to needlessly turn red and stop trains. That was, of course, the whole point.
Shunting Will Not Cause Crossing Gates to Fail to Drop
Shunting works by mimicking the presence of a train. In order to make crossing gates fail to drop, one must mimic the exact opposite: the absence of a train. Shunting will therefore cause lights and bells to activate, and gates to drop, if done on a block containing a grade crossing.
Suppose the railroad has some way to disable the crossing signals in such a situation, and chooses to do so. In this case, it is not the shunt that caused the signal to be disabled, it is the railroad. Moreover, there is still a phantom train on the block. In order to enter it, trains will have to stop, contact the dispatcher, and proceed through at a very slow speed.
If there is a way to disable the crossing signal, there will also be a way to re-enable it. Any failure to so re-enable the crossing signal after talking the train through the red light will thus be the fault of the railroad and not those placing the shunt.
Suppose that worst case happens anyhow. The train is only creeping through the crossing; it is not approaching at maximum speed. The train has a horn, and will still use it, so there will still be some indication of it.
The horror scenarios of trains sailing through crossings at full speed, with no advance warning whatsoever, as a result of shunts are therefore pure bullshit.
Shunting Does Not Typically Cause Emergency Stops
Railroads do not like emergency stops, because they often cause minor damage to the stopping train. The most common form of damage is flat spots on the wheels caused by them locking and skidding. (The affected wheels and axle must then be removed from the truck and turned back into round on a big lathe.) Sometimes the couplings between cars get damaged as well.
Since emergency stops are bad, railroad signals have indications in advance of occupied blocks, so that engineers will not encounter a red signal by surprise and instead be able to gradually bring the train to a routine stop. A shunt will cause these advance indications much the same as an actual train would.
The only way a shunt can cause an emergency stop is if one is placed on a block immediately in front of a running train, which will then see an unexpected red signal.
Emergency Stops Do Not Often Cause Derailments
The most frequent adverse consequences of them are, to reiterate, flat wheels and damaged couplings. Neither is a derailment. Neither endangers the public or the environment from errant rolling stock or spilled cargo.
Emergency stops are strongly correlated with derailments, but they do not typically cause them. Consider the following scenario: a rock slide blocks the tracks. The engineer rounds a bend and sees it, immediately putting his train into an emergency stop. It is hard to stop a train, so the train does not stop in time. It hits the slide and derails. There was both an emergency stop and a derailment, but the cause of the derailment was not the emergency stop.
Enter the PATRIOT Act
It is a huge piece of legislation hurriedly passed in the wake of the 9/11 attacks, containing enhanced penalties for just about anything that can conceivably be construed as terrorism. One of these things is tampering with railroad signaling systems. Installing an illegal shunt is a form of electrical tampering with a signaling system, therefore in the eyes of the law it is prosecutable as a terrorist act.
The main intent here was to prosecute other types of tampering, ones intended to produce false green signals that sent trains to their doom, but the way the law was written, any tampering is prosecutable.
Those Two Did Not Do Their Homework
But, fair or not, it doesn’t matter now. The law is the law, and it allows them to be aggressively prosecuted as terrorists for what they did.
If you are not willing to accept the consequences of something, you should not do it, whatever that something is. This is basic Direct Action 101 sort of stuff: always do your homework.
If you wish to make a point by stopping trains, there are ways to do it that, while still unlawful, do not entail the high legal risk that shunting does. It is not difficult to figure out some of these ways. Why needlessly expose oneself to legal risk? Why impose on one’s comrades the burden of defending against needlessly serious charges?
And that, not “terrorism,” is what those two saboteurs are really guilty of: failing to do their homework.