I’ve seen this in most local trains. They seem to be box shaped while bullet trains are more of an aerodynamic model.
In: Engineering
Well a bullet train tends to be pulling the same type of car behind it so the whole thing can be designed aerodynamically at once. And it needs to be aerodynamic to avoid turbulence from shaking things up to badly more.
Freight trains tend to be pulling cheap cargo containers that are just stacked onto a flatbed car, or flatbeds with lumpy cargo strapped down, or fuel tanks, etc. The point it they’re not exactly uniform. And the quality of the tracks isn’t set up to let them go fast in the first place so the benefits of good aerodynamics is just not important enough to spend money on.
Efficiency vs cost.
As your average speed goes up, energy required to maintain that speed goes up by a factor of 2.
At slow speeds the lack of efficiency doesn’t overcome the cost of engineering, and constructing complex aerodynamic shapes. As speed goes up, operating costs go up unless your efficiency increases as well.
Cheap trains go slow,
Aerodynamic drag increases with speed. a lot of trains don’t really go fast enough for that to be a huge issue.
In the US for example, most freight trains max out at around 60 mph. The bullet trains can go as fast as 200 mph.
That means that a freight train will have only about 8% of the drag a bullet train will have, before you account for the aerodynamic shape.
Bullet trains travel fast, so the air pushes back on it harder. Normal locomotives travel fairly slow and are more focused on power.
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