When automatic signal systems are removed from service, the operating environment reverts to that existing on 40% of the U.S. rail network: “dark territory.” How very 19th century. Indeed, the train control systems in dark territory are one or another iteration of the 19th century systems of “absolute block” or “manual block,” updated with radio technology to the 20th century’s track warrant control system. All of these are the legacy of the British “philosophy” that a single train cannot collide with itself. Seriously. Apparently the British had, once again, failed to account for Yankee Ingenuity.
The original version, “token block,” bestowed a symbol of authority, a token, upon a train to utilize the track. No other train could use that section until the token had been returned. The shadow of monarchy, with its token, a scepter representing sovereign authority, is preserved in the substance of British railroading.
A single train is given absolute authority to enter and utilize a section of track. That train becomes the “sovereign” in that block. This means that all switches that might allow for conflicting movement with our “sovereign” train must be known to be lined and locked for the sovereign and against the movement of any “pretender” train to the throne of authority.
