I set slow speed for the class 66 at ECW to 1.6 mph. It seems all is set up OK, but I see the speed increase much higher, even if the throttle is switched off completely, just due to the ramp it is on. It looks like the brake function is not implemented properly. It seems to happen consistently.
I've experienced the same when using the 66 on East Coast Way at the aggregate yard. I set the slow speed when filling the wagons and, as you say, it often increases well beyond the set speed, even with minimal or no throttle.
When I did these, I backed the the train through the loader, then set the speed set and filled the wagons heading forwards up the slope.
