Field Equipment
The system begins with passive transponders attached between the tracks which are electrically powered by an electromagnetic field when a locomotive passes over them. The transponders digitally convey their identification information and other relevant bits of information via wires to a trackside Base Station Controller (BCM), which uses a data radio to communicate with the locomotive’s on board computers, allowing the locomotives to know precisely when they have reached a particular waypoint. This location information is utilized by the on board systems when consulting its database of speed restrictions and track characteristics to calculate a real time braking curve.
As the locomotive proceeds down the track, the on board systems communicate via radio to the trackside BCMs in the region, requesting any temporary speed restrictions for the next three or more regions of the track, ensuring that the locomotive’s database is always kept current with any possible temporary restrictions issued by the train dispatcher. Wayside Communications Managers (WCM) (or packet switches) link all the BCMs in the region to a backhaul network which which allows them to communicate with the dispatcher's office and associated control systems via TCP/IP. This design provides locomotives with information about speed restrictions as soon as they go into effect without having to rely on voice communications with the train crew.
Additional BCMs (data radios) located at interlockings transmit information relating to absolute Stop signal indications and any speed restrictions pertaining to the train's route through said interlocking. Speed information acquired in this fashion will be displayed on the ACSES speed readout to supplement any speed information provided by the cab signaling system. After a positive stop the data radios will also transmit information releasing the train from the stop when track conditions permit. Such information about the status of the track occupancy, switch position, signal indication, and a host of other vital inputs—is accumulated by wayside encoders, such as a Safetran VIU-ACSES (see photo to the right), before being sent to the BCMs for transmission to locomotives.
The ACSES system also supports the use of temporary fixed transponders to enforce a temporary speed restrictions as an alternative or backup to using the wireless network. One transponder is placed a safe braking distance from the start of the to engage the restriction and a second is placed at the end of the restriction to release it.
Read more about this topic: Advanced Civil Speed Enforcement System
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