[2] The three surviving routes serve North and Northeast Philadelphia and connect with SEPTA's Market–Frankford rapid transit line.

The three Northeast Philadelphia trolley bus lines operating out of Frankford Depot, and the two South Philadelphia lines which operated out of Southern Depot, always existed in isolation from each other; there was never any trackless route or non-revenue 2-wire connection between those two networks.

Route 61-Ridge Avenue became a trolley bus line on October 5, 1941, converted from streetcar operation.

[4] PTC purchased 50 new, larger Brill trolley buses for this conversion, bought another 10 in 1942 and six vehicles from Pullman-Standard in 1944.

[5] The five trackless routes in place in mid-1961 continued to be served by trolley buses for the next four decades, and three remain so in 2025.

The rush hour service on route 66 includes several express trips, and one section of Frankford Avenue is equipped with a second set of trolleybus wires (in each direction) to enable trolley buses on express runs to pass those on local service.

[12] Until the retirement, in 2003, of the last trolley buses with rollsign-type destination signs, short-turn trips were indicated to riders by a red "slash" through the route number (known as a barré in British English, and barrata or barrato in Italy, where such practice was also common).

Also used on Philadelphia's streetcar routes, this practice was very uncommon on trolley buses in North America.

In the case of routes 59, 66 and 75, which are based at SEPTA's Frankford depot (garage), the initial reason for the conversion to buses was major reconstruction of the garage and the adjacent Market-Frankford "El" viaduct, and construction of a new Frankford Terminal.

That work necessitated the temporary removal of the overhead trolley wires used by trolley buses both at the garage and along the deadhead route (running along Frankford Avenue, directly beneath the El viaduct) connecting routes 59 and 75 to the garage.

[15] However, in early 2004 SEPTA began to consider reinstating trolley bus service at Frankford Division after the authority was informed that it would be required to repay some Federal Transit Administration (FTA) funds used in the 2002–2006 renovation of that garage (including renewal of the yard wires) and the adjacent route 66 terminal if trolley bus service did not resume.

[18] The pilot new low-floor trolley bus arrived in June 2007, for testing,[19] but not in passenger service.

With the conversion of the major Ridge Avenue route (61) to trolley buses in 1941, Philadelphia Transportation Company (PTC) again turned to Brill for the needed additional vehicles.

PTC purchased 60 Brill trolley coaches (as such vehicles were then commonly called in the U.S.[24]) in 1941–42, this time of the larger model 40SMT that the manufacturer had introduced in 1938.

A few retired Philadelphia trolley buses have been saved for historical preservation, including at public museums.

1947-built ACF-Brills 205 and 210 were acquired by the Shore Line Trolley Museum in 1981, when withdrawn from service in Philadelphia.

A few other ex-Philadelphia ACF-Brill and Marmon-Herrington trolley buses have been saved by private individuals, including one Marmon TC46.