A combination of wayside signal reporting, on board work reporting and message delievery along the railroad. Most commonly it is found along signaled/CTC rail lines and aids in the approximate location of trains, switch positions, route requests and other railroad specific data. A good source on monitoring ATCS data can be found on the ATCS Monitor website. ATCS data is not available on all railroads or lines. There is no standard channel plan or frequency band for ATCS. Listed are known channels in use, and will vary by railroad and/or location