by the Philadelphia City Planning Commission in 1960, under the leadership of Edmund Bacon. Such a tunnel would improve the connectivity of the network. The tunnel was constructed between 1976 and 1984 at a cost of $330 million. As part of the tunnel project SEPTA implemented a diametrical mode of operation. Heretofore the Pennsylvania and Reading trains had terminated in their respective terminals. Besides making transfers difficult, this led to congestion and reduced capacity. With the opening of the tunnel, Pennsylvania trains would run through the tunnel on to matched Reading lines, and vice versa. This would reduce congestion at the downtown stations, as very few trains would terminate or originate at them, and reduce the number of potential passenger transfers as each train reached more destinations. The original plan for the system was made by University of Pennsylvania professor Vukan Vuchic, based on the S-Bahn commuter rail systems in Germany. Numbers were assigned to the Pennsylvania lines in order from south (Airport) to northeast (Trenton); the Reading line matches were chosen to balance ridership, the physical characteristics of the lines, and the location of yards. An additional consideration was avoiding crossovers on the trunk lines. and to attempt to avoid trains running full on one side and then running mostly empty on the other. Vuchic recommended seven lines: Stage 1, which represented the state of affairs when the tunnel opened in 1984, was hampered by an "imbalance" between the Pennsylvania lines and Reading lines. Both the R3 and R4 would short turn at Wayne Junction or Suburban Station (as would some R7 trains), which cut against the diametrical principle. To correct this, Vuchich proposed the construction of a connection in the Swampoodle neighborhood between the ex-Pennsylvania Chestnut Hill West Line and the ex-Reading trunk line west of Wayne Junction as part of Stage 2, moving the Chestnut Hill West line to the "Reading" side. This connection was never built, leading (among other factors) to the following changes: R3 could not go to Chestnut Hill West, so R3 trains from Media/West Chester instead went to West Trenton along the R1. Service to Chestnut Hill West was picked up by the R8. R4 was dropped; The R5 Paoli runs local along its entire length most of the time, and Fox Chase became half of the R8. R8 was added for Fox Chase to Chestnut Hill West service, using the former R4-Fox