For my own layout, considering SP Coast Line traffic in 1953, I recognize significant auto parts and assembled automobile traffic. Auto assembly plants in both the Los Angeles area and in the Bay Area received most parts deliveries directly from plants predominantly in the east, but partial loads of parts were sent between plants via the Coast Line.
What plants are we talking about? Here is a list for 1953, probably not complete, but sufficient for my use.
Los Angeles: GM/Chevrolet in Van Nuys (called “Gemco” by SP) and also a Buick-Olds-Pontiac plant in South Gate; a Ford plant in Long Beach and a Lincoln-Mercury plant in what is now Commerce (Commerce didn’t become a city until 1960); Studebaker in Vernon; AMC/Nash in El Segundo; and Chrysler in Commerce.
Bay Area: GM/Chevrolet in Melrose (Oakland); Ford in Richmond; Chrysler in San Leandro.
Automobiles which were assembled at those plants were then shipped around the west, along with assembled cars coming from the east (mostly models of automobiles not assembled on the west coast). Thus there are two kinds of traffic: auto parts, much of it in specially equipped box cars; and finished automobiles, usually in double-door 50-foot cars. The loaded traffic, of course, is complemented and almost entirely balanced by empty equipment of the same type, moving in the opposite direction to return for reloading.
Specially-equipped cars, usually with loading racks, were extensively used for this traffic. The presence in a car of loading racks, which may or may not make the car unsuitable for general merchandise traffic, is indicated by a white stripe on the door (on the right door of a double-door car), at about 1/3 of the door height. Cars, which contain racks, so designed that they are stowable, permitting use of the car for merchandise loading, carry AAR class designation beginning with “XM”, as in XMR.
The car’s AAR class may also reflect fixed equipment, with such designations as XAP for auto parts. Most parts racks were not stowable. The 50-foot single-door cars were often in auto parts service. Typically the “stripe” (auto rack) cars, and any other cars in assigned service, are returned empty to origination point for reloading. Others are subject to confiscation for merchandise loading. Note that some regular XM cars are also used for parts loading.
West coast auto parts came primarily from the north-central Midwest area, along an arc from Buffalo to Milwaukee, centered on Detroit. Railroads along the service routing from these areas participated in car pooling, with each railroad contributing cars to the pool according to a formula, separately negotiated for each pool, which takes into account route miles, switching and terminal costs, and load origination and delivery revenues. Some traffic, however, was too light or variable to make a pool worthwhile, and originating railroads tended to provide the cars.
Shipments of auto parts typically moved on the Overland route to the Bay Area. For the Coast Line, this means Chicago-Detroit loads moving eastward (south), with empties in the reverse direction. Loads bound to Los Angeles from the upper Midwest and Detroit tended to be routed through St. Louis for Cotton Belt’s “Motor Special” to LA, but sometimes also moved by the Golden State route. Some part inventories were also equalized between the GM and Ford plants in LA and the Bay Area.
The other side of the auto traffic is assembled or set-up cars. Most assembled automobiles delivered to the West Coast originated in Detroit and moved via Chicago onto the Overland route, or were shipped from St. Louis or Kansas City, and moved, respectively, over the Cotton Belt and Golden State routes, giving Coast Line loads in both directions. Cars assembled in LA or the Bay Area may also move in either direction for eventual delivery in various parts of the west. This includes Ford automobiles assembled at Long Beach, served by ATSF, which were shipped in ATSF auto cars for Coast Line destinations.
Those interested in this traffic may benefit from the Walthers book, America’s Driving Force: Modeling Railroads and the Automotive Industry, Walthers, Milwaukee, 1998. The book is out of print, but can usually be found at used book dealers on the Internet. It does not contain great detail about the 1950s, however.
Modeling needs: this is almost all mainline traffic, not traffic on my branch line. The intent is to have mostly 50-foot long cars, to reflect post-World War II practice, and (by AAR definition) double-door. Rather less than half should be designated auto parts, just because the bulk of AP traffic arrives directly in LA or the Bay Area. Many parts cars are lettered for appropriate originating roads (C&O, GTW, DT&I, NYC, PM, PRR, WAB) or from pool roads (ATSF, MP, NKP, RI, SSW, SP and UP) for eastern traffic, as well as SP and ATSF cars for western traffic.
In addition, some regular XM cars are in parts service, while some “auto cars” (meaning double doors, in AAR parlance) are classified XM or XMR and can be used for merchandise. Cars designated XAP or XAR cannot be used for other than auto parts or automobile shipping assignment. Cars classed XML are largely PD cars or equivalent, and would probably be restricted to auto parts.
Until more operation with symbol freights takes place, exact numbers needed cannot be identified, but preliminary planning includes 1 each C&O, GTW, NKP, MP, NYC, PM, PRR, RI, SSW, UP and WAB; 2 DT&I, 2 ATSF, and 5 SP. Total cars, 20. Probably an additional Cotton Belt car should be added to this list, possibly also C&NW. Most are 50-foot double-door cars, with a few 40-foot double-door cars and 50-foot single-door cars, all of which can be mixed in cuts of auto cars.
Here are some of the models already in service, concentrating on the SP cars since this is mostly an SP blog. First, the old Athearn double-door car, with wrong numbers of both side panels and roof panels, but an “okay” stand-in for the time being. It’s been modified with a straight side sill and wood running board, and various detail upgrades (including removing the door “claws”). It represents Class A-50-12 with auto racks (AAR class XMR), thus the white door stripe. It will be restricted to my main line.
Cotton Belt was an important partner for SP and T&NO in premium auto parts and automobile traffic. I have one such car on the layout, a Sunshine model of an XMR car.
A correct SP car and one which is important for this service is the Class B-50-22 car for auto parts. Here’s the Proto2000 version, almost exactly accurate right out of the box. By AAR definition this is a box car, not an automobile car, but is part of the automobile traffic fleet. It carries AAR class XME (stowable parts racks).
Finally, another car which is close to correct but has too-narrow side doors, the Red Caboose representation of Class A-50-13. I regard it as an acceptable stand-in but do plan to replace it eventually with the Sunshine resin version. This particular car is AAR class XMR, thus the white door stripe.
If anything, I have too big a fleet of automobile and parts cars, but they will provide variety in my auto-traffic cuts in mainline trains. And there may occasionally be that delivery of a couple of sedans at the freight house for a local auto dealer . . .