Live video programmes can bring in better travel experience for subway passengers and earn abundant advertisement revenue for subway operators. However, because the train-trackside channels for video dissemination are easily accessible to anyone, the video traffic are vulnerable to attacks which may cause deadly tragedies. This paper presents a situation-aware authenticated video broadcasting scheme in the railway network which consists of train, on-board sensor, trackside GSM-R (Global System for Mobile Communications-Railway) device, WiFi AP (Access Point), and train control center. Specifically, the scheme has four modules: (1) a train uses its on-board sensors to obtain its speed, location, and RSSI (Received Signal Strength Indicator) of train-trackside WiFi channel; (2) the train reports these real-time measurements to the railway control center with the legacy GSM-R networks; (3) according to the measurements, the control center or its WiFi AP adaptively customizes the protected codestream bitrate and AP-train handover time; (4) the train renders the received codestream which passes the authenticity verification process. As shown in the performance analysis, the present scheme ensures the codestream authenticity and provides high QoS (Quality of Service) in the lossy subway WiFi environment.