Modelers don’t always include the ideas of express shipments in their operating schemes. By “express,” in railroad terms, is primarily meant Railway Express Agency traffic, but also includes various expedited traffic, mostly LCL (Less than Car Load) in character, moved by the railroad. I want to say a little about the Southern Pacific aspects of this.
The majority of this traffic naturally moved in baggage cars, actually termed “baggage-express” or BE types by AAR. And most such traffic visible on a particular railroad would be in the cars of that railroad. But longer-distance movements did cause the movement of off-road baggage cars onto neighboring or even far-away railroads. So modeled head-end consists can certainly include foreign baggage cars.
I remember as a boy, viewing the Postal Annex and REA buildings at Los Angeles Union Passenger Terminal (LAUPT), with plenty of cars belonging to the three railroads that used LAUPT, SP, Santa Fe, and Union Pacific, but there were almost always some Missouri Pacific or Texas & Pacific cars in blue and light gray, often Burlington and Rock Island cars, and sometimes New York Central and Pennsylvania cars. All but the last two were, of course, connections of the SP and UP, and Santa Fe connected with all of them, the last two in Chicago.
This means that both baggage cars, and head-end express box cars, of connecting roads would show up occasionally in SP trains, such as the ones I operate on the Coast Route main line on my layout. I can show a few examples. Below is a train with SP express box 5749 (Beaver Creek brass) at the head end, followed by CB&Q 8796, a wartime troop car converted to baggage service (made from a Walthers car by Richard Hendrickson). On the head end is Class P-10 Pacific 2485 (Precision Scale brass).
Another example would be a consist like the one below, again with Pacific 2485, this time with an older SP express box, SP 5857 (Sunshine resin), Class BX-50-15, followed by Rock Island 20062, one of the aluminum box cars Rock Island bought for this kind of service (Sunshine resin). The two box cars are followed by SP 6448, kitbashed from Athearn cars, to represent Class 70-B-9.
The 70-B-9 car project was described in some detail for Prototype Modeler magazine (Vol. 7, No. 6, March-April 1984, pages 39–44). What I obtained was a car with correct windows and reasonable looking doors and other details. I used the Utility vents typical of SP classes 70-B-9 and -10 for the model.
I have occasionally been asked whether SP used “LCL cars” to pick up and deliver local package freight. Many railroads did this; Tony Koester’s Nickel Plate Road layout famously does so in its local trains, with such a car behind the power. The photo below (Tony Koester) shows an example.
But SP owned a trucking subsidiary, Pacific Motor Trucking or PMT, that did this kind of local pick up and delivery. So trains didn’t carry LCL cars, and instead an SP layout from the transition era ought to show traffic like this on its roads, in this case Pismo Dunes Road on my layout (model painted by Jim Elliott). I’ve discussed this before (see an example at: https://modelingthesp.blogspot.com/2022/01/overnight-box-cars-part-2.html ).
What about the famous SP “Overnight” cars? They were certainly in LCL service, and intended for high-speed operation. Both the famous post-World War II paint scheme of black with a red and yellow “overnight” symbol, and the pre-war schemes were described in an earlier post (you can find that post at: https://modelingthesp.blogspot.com/2022/01/the-overnight-box-cars.html ).
Very occasionally, these cars did have local destinations, instead of their usual Los Angeles-San Francisco routing. This one, SP 97954, built from a Sunshine resin kit, is spotted on the house track in my layout town of Ballard (and note the PMT truck on Bromela Road in the background).
Recognizing express and LCL traffic should definitely be part of any layout operating scheme, and research may be needed to understand the patterns of any particular railroad and locale.