This increased the capacity of the above-water portion of the facility to four lanes, facilitated needed repairs, and helped insure against a total closure should a trestle be struck by a ship or otherwise damaged (which had occurred twice in the past).
By increasing the capacity of the facility's above-water section to four lanes, repairs could be carried out, and the risk of a total closure due to a trestle being struck by a ship or damaged was reduced (an event that had occurred twice before).