Surely this must be a bug? But I'm no expert On Hauptsrecke Rhein Ruhr running the scenario Snow Time - S-0Bahn train in (insurprisingly) snowy conditions. If you accelerate at say 25% power, train starts moving. The hammer it to 90% causing the wheels spin. At this point HUD and train Speedo leap to 90km/h. The train is still accelerating with sounds to reflect that. If you decrease the power to say 85% (wheels still spinning), the speedos show 85km/h. They reflect the power setting. Once the train hits 85km/h, the train starts to accelerate more and shows the increasing speed. A similar thing occurs on braking. Say you are doing 100km/h. Brakes on and then to 100%. Speedo/HUD show a speed of 0km/h, train is decelerating AND the braking sound has gone completely. Train will come to a stop. But you have no idea how fast you are going. Whilst in this odd (at least to me) 0km/h state, if you release the brakes some to stop the sliding, speedo jumps up to the correct speed and the sound reappears. So is this expected/correct behaviour? This is with a version that updated on the 3rd Feb
The speedo is reading off the rpm of the axles, not the earth. If the wheels are spinning out of control, the speedo will tell you you're doing 1000 mph. Short answer- don't go above 70% power in the snow.
If the axles quit spinning, the speedometer will say you are doing 0, but the train is sliding at whatever speed you had before you locked your wheels. And since steel on steel slides very well, it will take you much longer to stop, just like locking up your brakes and sloughing rubber off your tires... except a much more annoying sound to be sure..... edit: changed from “quick spinning” to “quit spinning”.