A method for determining a slack condition of a vehicle system includes determining when each of first and second vehicles reaches a designated location along a route. The method also includes communicating a response message from the second vehicle to the first vehicle responsive to the second vehicle reaching the designated location, calculating a separation distance between the first vehicle and the second vehicle based on a time delay between a first time when the first vehicle reached the designated location and a second time when the second vehicle reached the designated location, and determining a slack condition of the vehicle system based on the separation distance. The slack condition is representative of an amount of slack in the vehicle system between the first and second vehicles.