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?

As far as I am aware, CFrames 'set' a part's location, whilst Vector3s 'move' its location. Try attaching the player to the seat, or using Vector3s and .position instead of CFrames.