[vvanders]

Not just torque, traction too.

VFD AC motors will intrinsically self-correct for overspeed when static traction slips and starts going into dynamic region (due to the frequency being slower than the slip/overspeed) and re-enter static friction region. DC or ICE will react to the lack of traction by turning faster as you hit the dynamic friction region and "spin out". Traction control is always reactive and lags behind. Last I read the difference in traction on rail for AC vs DC was on the order of 50%(!).

It's also why EV cars have stupidly awesome traction in adverse conditions under acceleration, trains had been perfecting that technology for decades.