Standard Code of 1912: Classic Railroad Signals

America’s rail network is one of the most underrated technologies in the country, and it has a fascinating history in its use of railroad signals. Brian Solomon’s book Classic Railroad Signals explores the usage of these signals throughout history and in present day. The following excerpt from Solomon’s book takes a look at the advancements made early on with the Standard Code of 1912. Pretty cool stuff!

Standard Code of 1912
In 1912, after years of discussion, the American Railway Association and Railway Signal Association agreed to a practical and limited number of aspects based on daytime three-position semaphore positions. Provisions for equivalent aspects were also included for two-position, lower-quadrant signaling. While ARA had advised the R-Y-G color progression since 1896, in the 1912 codebook this arrangement was more strongly encouraged.

Some signal hardware has enjoyed exceptional longevity. This General Railway Signal Company Model 2A semaphore was installed by the Monon before World War I and was still in service on CSX in June 2010, nearly a century later. Brian Solomon

Significantly, the code offered three signaling schemes (all based on the standard three-position semaphore aspects) with which railroads could base their rulebooks. Each scheme was based on the number of semaphore arms employed:
Scheme one was the most basic, based on single-arm signals to provide the three most common aspects: horizontal blade indicating “Stop”; 45-degree blade indicating “Proceed With Caution”; and an upright (vertical blade) indicating “Proceed.”

Scheme two used two arm signals and offered simple speed signaling with five indications and eight aspects. When a signal scheme uses multiple blades and/or when ground level signals (known as dwarfs) are used, more than one aspect may be used for the same indication. “Stop” for example, may be displayed by either one horizontal arm or two, or a dwarf semaphore displaying a horizontal. Five of the eight aspects used twin-arm signals; the top arm signified a normal speed route, while the lower arm was used for routes less than normal speed (usually diverging from the main route) and the actual speeds were left up to the railroad.

Aspects included: horizontal blade over a 45-degree blade indicated “Proceed at low speed” (in other words proceed on a diverging slow speed route); horizontal over a vertical indicated “Proceed at medium speed”; and vertical blade over a horizontal blade could be used for “Proceed” (on normal speed route) and thus shared this indication with a single vertical arm. Scheme three followed a similar progression using three arm signals for speed signaling. This
featured eight indications and twenty aspects.

A view made shortly after sunrise on July 17, 2008, shows Union Switch & Signal searchlights at the west end of Alford Siding (Alford, Oregon) on Union Pacific’s former Southern Pacific Cascade Route. Southern Pacific designated all of its lines on an east–west axis. Regardless of compass direction, the direction of travel toward its San Francisco headquarters was always “west.” As a result, SP’s Cascade Route was viewed as an east–west operation despite its largely north–south alignment. Scott Lothes

One-, two-, and three-arm tall signals and dwarfs all displayed “Stop,” so there were four aspects for “Stop” covering all combinations of semaphore arms, and in all the aspects arms were displayed horizontally. Three additional indications were: “Proceed with caution on low speed route”; “Proceed with caution on medium speed route”; and “Reduce to medium speed.” This scheme enabled combining interlocking and automatic block aspects, while allowing considerable signaling flexibility for complex junctions where track capacity was often pushed to its practical limits.

In 1928 the ARA restandardized the standard code, introducing standard names for aspects and revised indications and rules. Changes covered provisions for new types of light signals including position lights and color position light hardware. In 1938 and again in 1949, the Association of American Railroads (successor to the ARA) made further revisions to its signal code. The rule numbers, aspects, and indications from this period are similar to those still in use today, although continued refinement has resulted in a great number of changes.

Explore the history, quirks, and stories behind signals with gorgeous period and contemporary photography.

Railroad signals are the link between the steam era and modern railroading. Designed for reliability and durability, signals can survive for decades. In fact, old semaphores installed during the early years of the twentieth century were still in service during the 1990s, protecting trains that were running with the latest modern diesels. Even searchlight-style signals that were the epitome of 1940s railroading continue to work today.

Though standards were introduced in the early twentieth century, interpretation varied greatly among railroads, so even major railroads have individualized signals. Some, such as the Pennsylvania Railroad, were noted for their distinctive signaling hardware. Others lines became known for their peculiarities in practice.

Classic Railroad Signals examines how different railroads developed specific hardware to serve their unique needs, in the process tracing the lineage of various types of hardware and highlighting how and where they were used. From nineteenth-century mechanical signals to disc signals, upper- and lower-quadrant semaphores, three-light electric signals, searchlight-style targets, positional lights, and color-position light hardware, author Brian Solomon covers nearly every conceivable piece of North American signaling hardware, even the virtually extinct wig wag that was once standard in California and Wisconsin.

Gorgeous period and contemporary photography shows signals and trains from around North America. Classic Railroad Signals should be next to Railroad Signaling on every railroad fan’s bookshelf.