Automobile traffic increased dramatically in the ensuing decades while the Key System declined, and in October 1963, the Bay Bridge was reconfigured with five lanes of westbound traffic on the upper deck and five lanes of eastbound traffic on the lower deck. The Key System originally planned to end train operations in 1948 when it replaced its streetcars with buses, but Caltrans did not approve of this. Trucks were allowed on both decks and the railroad was removed. Owing to a lack of clearance for trucks through the upper-deck portion of the Yerba Buena tunnel, it was necessary to lower the elevation of the upper deck where it passes through the tunnel, and to correspondingly excavate to lower the elevation of the lower portion. Additionally, the upper deck was retrofitted to handle the increased loads due to trucks, with understringers added and prestressing added to the bottom of the floor beams. This retrofit is still in place and is visible to Eastbound traffic.