-- server script 

local train = game.Workspace.Train

​

local speed = 0

​

train:GetPropertyChangedSignal("Speed"):Connect(function()

    speed = train.Speed

end)

​

local function moveTrain(direction)

    if direction == "forward" then

        speed = speed + 0.5

    elseif direction == "backward" then

        speed = speed - 0.5

    end

    train.Speed = speed

end

​

game.ReplicatedStorage.TrainControl.OnServerEvent:Connect(moveTrain)