How do I get the Current Speed of A VehicleSeat?

So I have a car that has a GUI in it with a Speedometer and I want to obtain the current speed of the vehicle seat. Hoever, it does not show when I try to set the label text below to that seat? How do I do that

wait(1)
game.Players.LocalPlayer.PlayerGui.YavinGUI.YavinDash.Speedometer.Text = tostring(script.Parent.Velocity.X)