The value of the transient resistance "wheel — rail" is the determining factor for ensuring the shunt effect of track circuits. Taking into account the severity of consequences of failure to ensure the shunt effect — accidents or train derailments due to a switch being thrown under a train or opening of a traffic light fencing an occupied track section, continuous monitoring of the condition of track circuits (shunt sensitivity) is necessary for timely detection of critical values of destabilising factors or operating conditions. The article discusses ways to automate measurements of train shunt resistance and ways to prevent shunt loss (non-fulfillment of the shunt effect) by an occupied track circuit. The work also examines the possibility of implementing continuous monitoring of the shunt effect (monitoring of shunt sensitivity) based on a model of changing the values of their parameters during the movement of rolling units along a rail line. The obtained results can be used to solve such analytical and practical problems as: calculation and investigation of the dynamics of change in the sensitivity coefficient of the track circuit to the actual train shunt; construction of a classifier of the track circuit states invariant to external perturbations during the train movement from the moment of entry to the moment of release of the rail line; organisation of continuous monitoring of the shunt sensitivity of the track circuit.