But the renovation may cause even more serious congestion of the tunnels .
But the renovation may change the starting time for one - tube - two - way traffic ( using one tube only for both direction of traffic ) from 12 am to 9 or 10 pm .
But the renovation may cause even more serious congestion of the tunnels and may change the starting time for one - tube - two - way traffic ( using one tube only for both direction of traffic ) from 12 am to 9 or 10 pm .