Why are jet engines not used in trains?

All the other answers are correct, but overlook something else important. Jet engines (more properly gas turbines) require a lot of maintenance. read more

I think both implementations show that one problem is how you upscale the technology to power a much larger train. But jet engines are (essentially) a form of gas turbine which have appeared in a number of experimental trains British Rail APT-E Turbotrain the articles will give you some of the reasons why they haven't been widely adopted. read more

The reason they are not used in locomotives can be boiled down to the fact that the difference in fuel consumption between peak power output and low power output of a turbine engine is small, due to the minimum requirements to simply keep the engine running at idle. read more

Turbine engines use as much as 65% of their overall generated power to run the compressor at the front of the engine. This means that when the engine is set to idle, with no net energy output, the engine is still burning 65% of the fuel it would at full speed. read more