A driving situation detection system capable of detecting driving situations swiftly with high reliability is obtained. The driving situation detection system includes real curve arithmetic means reference vehicle model and observer means, a differentiator unit, a model curve radius arithmetic means, and an assessment unit. The arithmetic means generates real curve radius signals based on wheel speeds. The reference vehicle model and observer means processes input signals utilizing a linear reference model to generate a yaw rate signal and a vehicle body side slip angle signal. The unit differentiates the vehicle body side slip angle signal to generate a vehicle body side slip rate signal. The model curve radius arithmetic means generates a model curve radius signal based on the yaw rate signal and the vehicle body side slip rate signal. The assessment unit detects undesirable driving situations by comparing the real curve radius and the model curve radius.