A question from a SEPTA noob

firthorfifth06 wrote:Was there ever an R4?

Original route numbering plan

The original Regional Rail plan with R1 to R7Regional Rail lines are numbered from R1 to R8, with the notable omission of R4. The reasons for this are rather complicated, going back to the original planning stages.

Part of the planning for the Center City Commuter Connection was to decide on how trains would be routed through the tunnel and which branches would be paired up.

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 PRR-side lines in order from south (Airport) to northeast (Trenton), and the RDG-side matches were chosen to roughly balance ridership, to attempt to avoid trains running full on one side and then running mostly empty on the other. The following lines were recommended:

R1 Airport to West Trenton
R2 Marcus Hook (now Newark) to Warminster
R3 Media/West Chester (now Elwyn) to Chestnut Hill West
R4 Bryn Mawr (on the same tracks as the R5 Paoli) to Fox Chase
R5 Paoli (now Thorndale) to Lansdale/Doylestown - express from Center City to Bryn Mawr, with R4 running local
R6 Ivy Ridge (now Cynwyd) to Norristown
R7 Trenton to Chestnut Hill East
In addition to the Center City Commuter Connection, it was assumed that SEPTA would build one more connection, the Swampoodle Connection. This would allow PRR-side trains from Chestnut Hill West to join the RDG Norristown line instead of the PRR mainline at North Philadelphia station. The Chestnut Hill West line and the Norristown line run adjacent to each other at that point, in the Philadelphia neighborhood of Swampoodle. The Swampoodle 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 Chase and R3-Chestnut Hill West halves.
One of the assumptions in this plan was that ridership would increase after the connection was open. Instead, ridership dropped after the 1983 strike and has to this day never regained the 1970s levels. Because of this, most trains are 2 or 3 car lengths, with trains on many routes running mostly empty during the midday and evenings, and pairing up based on ridership is less relevant today.

Several expansion plans have proposed using the R4 designation for a new line.

At a later time, R1 was applied to the former RDG tracks, shared with the R2 and R5 lines to Glenside (SEPTA station), and R3 to Jenkintown, and R1-Airport trains ran to Glenside rather than becoming R3 trains to West Trenton. In later years, SEPTA became more flexible, and now a decent number of trains change number designations downtown to cope with differences in ridership on various lines.

Since the original service, the following termini have changed:

R2 - Marcus Hook was extended to Wilmington and Newark
R3 - West Chester was cut back to Elwyn
R5 - Paoli was extended to Downingtown and Parkesburg, then later cut back to Downingtown, and later re-extended to Thorndale
R6 - Ivy Ridge was cut back to Cynwyd