Diesel-electric locomotives solve the what-about-when-you-don’t-need-power-problem with large resistors to convert generator output to heat. Any other solution

Diesel-electric locomotives solve the what-about-when-you-don’t-need-power-problem with large resistors to convert generator output to heat. Any other solution is non-trivially more complex. Because you need to be able to slam your brakes and then punch the throttle. Dedicated right-of-way means trains don’t operate in rush hour traffic and infrastructure costs dominate their economics. Dedicated right-of-way is also a good way to improve bus efficiency, but nobody wants to pay the political price for that infrastructure.