Cab signalling
From Wikipedia, the free encyclopedia
Cab signalling refers to a railroad safety system which communicates track status information to the train cab, where the engineer or driver can see the information, and where an automatic system can apply the brakes and bring the train to a stop if a dangerous condition occurs. These systems range from very simple coded track circuits to transponders that communicate with the cab.
[edit] SEPTA cab signalling
The Southeastern Pennsylvania Transportation Authority (SEPTA) uses a four-aspec cab signal system, and the techinical specification for the Silverliner V includes a description of the cab signal system, which uses coded track circuits to transmit an audio frequency electrical signal along the tracks that is picked up by inductive pickups mounted just above the rail at the front of the train. The system uses two frequencies, 100 Hertz and 250 Hertz, which are modulated at different rates to convey signal information. [1] A summary of the codes and speeds appears at [2].
[edit] Positive train control
Positive train control systems can be overlaid onto cab signal systems or can replace them altogether. These include the Incremental Train Control System (ITCS) installed by GE on the Chicago-Detroit route in Michigan and the North American Joint Positive Train Control (NAJPTC) system being testing in Illinois on the Chicago-St. Louis route. The ITCS has been in revenue service since 2002 with speeds up to 90 MPH.[3] Other systems include Alaska Railroad's CAS, CSX's CBTM, and BNSF's ETMS.
