my thought so far: pre-ww2, probably late 20s, there would have been some public-private measure to connect the subway terminal and main street terminal with thru-running tracks. it would be panned as a corrupt handout to a failing company, but it would have passed the city council vote somehow or other.

In 1940, the san fernando valley line would have been realigned into the hollywood freeway median, forming a near-continuously grade separated trunk from san pedro street to north hollywood.

Although the PE wouldn't use the thru tracks much in revenue service, postwar they would be considered an important asset by the city, as they would allow for consolidating train maintenance to a single yard and getting rid of older equipment.

When the LAMTA was formed to buy out the old transit systems and study a north-south monorail, they would opt to instead keep running the long beach-SFV service while shedding the underused bellflower branch and slower glendale and monrovia lines.

The trunk would limp along thru the 60s, with even basic maintenance being merely tolerated by city leaders. ridership would slowly fall as the tracks aged, trip times lengthened, and freeways expanded.

The system would finally get some attention in the Tom Bradley era, with major track upgrades, the acquisition of an SPRR right of way to form a west SFV branch, a new glendale branch, streamlining of the long beach line to partly follow the river with new park-n-ride stations, and an airport service using the old el segundo branch. Maybe it would even be rebranded as some sort of Rapid Transit!

Still, it would suffer from similar challenges as contemporary legacy streetcars in growing cities. Outdated signalling limited service levels, and the schedules were complex and byzantine. It would probably get Boeing SLRV's.

This whole time, the system would have remained wholly inaccessible, with high-floor trains and low-platform stations. Many platforms were only connected to street level by stairs. Accessibility would become a pressing concern thanks to activism throughout the 70s.

Late in his administration, Bradley wanted the demanded accessibility overhauls to be a prestige project for him, but they lagged behind their ambitious schedules. The system became even more confusing, with some stations accessible and others not.

Simultaneously, LAMTA was also pursuing an all-new subway system, consisting of an east-west line from UCLA and the wilshire corridor to East LA, and a north-south line from West Hollywood to Harbor City. These plans would be shelved when Richard Riordan took office in 1993.