How to make my bike work on Touch Device?

I want to convert this bike from the standard WASD to work on the Roblox Mobile D-Pad. Does anyone know what the inputs are for each direction?

Cheers,

Michael.

        if Key == "w" then
            Forwards = true
            while Forwards do
                CurrentSpeed = math.min(70, (CurrentSpeed + (Acceleration * (1 / 30))))
                wait(1 / 30)
            end