Obscure Externalities – Coal Edition

Coal trains in Wyoming. Photo: KimonBerlin via Flickr/CC BY 2.0

The negative externalities of fossil fuels and coal in particular are fairly obvious and range from its effects on individual health to climate change impacts. But here’s one I hadn’t thought of. Via Pedestrian Observations we learn that coal shipping slows down cargo and passenger rail service in three distinct ways.
– First is the non-surprising fact that coals trains are large and slow. In order to be shipped profitably, coal trains tend to be larger than most freight trains and operate at slower speeds. Even though they may be limited to being on the rails to specific times of day, this still reduces the amount of time for faster freight and passenger service and reduces the speed that other trains can move at when the coal is on the track.

– More obscurely, routes that carry coal must be laid out to handle these larger, slower trains. Specifically, turns cannot be banked as steeply. Banked turns allow a vehicle to negotiate a curve at a higher speed without risking the cargo shifting excessively or unnecessarily causing discomfort to passengers. Beyond the fact that freight is slower and needs a lower banking, extra heavy freight is at more risk from shifting loads causing a crash and so banking must be even lower. All of this slows down all trains no matter what their top speed is.

– Finally there is just the damage to the rails that heavy loads cause to the tracks. Much as in the way that road damage goes up exponentially with the weight of the vehicle (so a 4 ton truck causes 4 times as much wear to a road as a 2 ton car), extremely heavy trains cause significantly more wear and tear than standard cargo and especially passenger trains. Poor track conditions force the fastest trains to be even slower again so this costs both time and higher maintenance costs.

Now, most of these issues are just built in to the fact that in most places freight and passenger trains share tracks. A few less coal trains is not going to change that fundamental limitation to passenger rail in the US. But even minor improvements to the speed of standard freight has benefits, increasing its competitive edge over less efficient truck shipping, improving supply chains, etc. Fewer large, slow trains and tracks in better condition will benefit all other rail traffic.

This will not be the straw that breaks the camel’s back on coal based power generation. But it is a good reminder of the many large and small ways that transitioning away from coal will benefit us in varied ways.

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