CFrame seat movement leaves player behind, what is wrong?

So I have this script that moves a model that contains a train model and a sea when W is pressed.Everything works fine except for the fact that the player is left behind when the train is moving.

seat = script.Parent
tram = script.Parent.Parent
plr = seat.Occupant

while true do
    if seat.Occupant ~= nil then
        print("sitting")
        seat.Occupant.Parent.isDriving.Value = true
        print (tram.forward.Value)
        while tram.forward.Value == true do
            --print(tram.tram.Position)
            --seat.Position = seat.Position + Vector3.new(0, 0, -1)
            --tram.Position = tram.Position + Vector3.new(0, 0, -1)
            tram:SetPrimaryPartCFrame(tram:GetPrimaryPartCFrame() * CFrame.new(0,0,-1))
            --seat.Occupant.Parent.HumanoidRootPart.Position = seat.Position
            wait()
        end

        while tram.backward.Value == true do
            wait()
        end
    end
    wait()  
end

What am I doing wrong?