Monitoring device (100, 200) for a rail system (230, 330, 430, 530), in particular for a rail route (238, 338, 438, 538) of the rail system (230, 330, 430, 530) that is equipped only with a balise-based train control system, comprising: - a train detection receiver module (102, 202) configured to receive a train presence signal from at least one train presence sensor (234, 334, 434, 534) located in a defined rail area (236, 336, 436, 536) of the rail system (230, 330, 430, 530), - a balise receiver module (104, 204) configured to receive a balise excitation signal of a first balise (232, 332, 432, 532) arranged in the defined rail area (236, 336, 436, 536), and - at least one determination module (106, 206) configured to determine if the balise excitation signal and/or the train presence signal are received, - wherein the monitoring device (100, 200) comprises at least one detection module (108, 208) configured to at least determine that a non-balise-capable rail vehicle (244, 344, 444, 544) has passed the defined rail area (236, 336, 436, 536) if it is determined that only the train presence signal is received, - wherein the detection module (108, 208) is configured to detect that a balise-capable rail vehicle (244, 344, 444, 544) has passed the defined rail area (236, 336, 436, 536) if it is determined that the train presence signal and the balise excitation signal are received, characterized in that the determining module (106, 206) is configured to determine whether the balise excitation signal and the train presence signal are received, based on a synchronism criterion, wherein the synchronism criterion specifies that the balise excitation signal and the train presence signal must be received within a specific time window, wherein it is provided that the balise excitation signal must be received at least when the train presence signal is also received, and wherein only if both signals are received at the same time is it determined that a balise excitation signal and a train presence signal are received, and if that is not the case, it is determined that only the train presence signal is received. - a train detection receiver module (102, 202) configured to receive a train presence signal from at least one train presence sensor (234, 334, 434, 534) located in a defined rail area (236, 336, 436, 536) of the rail system (230, 330, 430, 530), - a balise receiver module (104, 204) configured to receive a balise excitation signal of a first balise (232, 332, 432, 532) arranged in the defined rail area (236, 336, 436, 536), and - at least one determination module (106, 206) configured to determine if the balise excitation signal and/or the train presence signal are received, - wherein the monitoring device (100, 200) comprises at least one detection module (108, 208) configured to at least determine that a non-balise-capable rail vehicle (244, 344, 444, 544) has passed the defined rail area (236, 336, 436, 536) if it is determined that only the train presence signal is received, - wherein the detection module (108, 208) is configured to detect that a balise-capable rail vehicle (244, 344, 444, 544) has passed the defined rail area (236, 336, 436, 536) if it is determined that the train presence signal and the balise excitation signal are received, characterized in that the determining module (106, 206) is configured to determine whether the balise excitation signal and the train presence signal are received, based on a synchronism criterion, wherein the synchronism criterion specifies that the balise excitation signal and the train presence signal must be received within a specific time window, wherein it is provided that the balise excitation signal must be received at least when the train presence signal is also received, and wherein only if both signals are received at the same time is it determined that a balise excitation signal and a train presence signal are received, and if that is not the case, it is determined that only the train presence signal is received.