Incremental Train Control System (ITCS), developed by General Electric Transportation Systems (GETS), is a communication-based signaling system overlaid on an existing signal system. This is one class of PTC that was designed to prevent train collisions and overspeed derailments. FRA, Amtrak and the Michigan Department of Transportation cooperated to initiate the upgrading of 66 miles of the Amtrak-owned Michigan Line between Kalamazoo and New Buffalo, Michigan, to allow 110-mph operation with this PTC system. The program started in 1996 with a contract for Harmon Electronics, which has since been acquired by General Electric, to develop the first ITCS demonstration on this corridor. ITCS remains in place and active on this route today.

The main function of the system is to enforce signal authorities, civil speed limits and temporary speed limits. It was designed as a vital overlay to an existing Centralized Train Control (CTC) system with a wireless computer network of servers along these 66 miles. These servers communicate with the equipped locomotives using an Ultra High Frequency (UHF) radio network based on Advanced Train Control System (ATCS) Spec 200 frequencies.

Unique to this system is the employment of a TDMA (Time Division Multiple Access) scheme to prevent radio messages from interfering with each other. With this scheme, the servers can more easily communicate with many locomotives. Unlike an office-centric system like the Illinois Department of Transportation (IDOT) PTC, all the communication tasks are performed locally device-to-device. Host processors on board locomotives make most of the decisions. However, a computer in the office is necessary to transmit temporary speed restrictions to the server and to download the health of the system when it is necessary. This train tracking system is based on the Global Positioning System (GPS).

ITCS is a vital system, meaning that it will ensure that all the messages are delivered properly and accurately, and that it will continuously perform surveillance of all devices and interfaces of the system to ensure that they are in proper working condition.  If not, a fail-safe fall back will be enforced. Another feature that is critical to high-speed operation is the advanced grade crossing activation. When the train approaches a crossing, continuous location tracking and calculation are performed and the crossing gates will be activated using wireless communication, instead of the conventional track circuit, at the appropriate time to ensure the optimum advanced activation time.

The system has been in revenue service since September 2000. At the beginning, the speed limit of 79 mph was kept to gain experience and confidence with the system. The maximum speed limit was subsequently raised to 90 mph in January 2002, then to 95 mph in September 2005, then to 110 mph in February 2012.