At around 21:43 hrs on Sunday 21 June 2020, a near miss occurred between two passenger trains at London Underground’s Chalfont & Latimer station on the Metropolitan line. A few minutes earlier a southbound Chiltern Railways train had passed a signal displaying a red (stop) aspect (known as a signal passed at danger or a ‘SPAD’). This resulted in the train being automatically stopped by a safety system, known as a tripcock, which had applied the train’s emergency brake. Without seeking the authority required from the service operator (signaller), the driver reset the tripcock before continuing towards Chalfont & Latimer station, where the train was routed towards the northbound platform, which was occupied by a London Underground train.
The Chiltern Railways train stopped about 23 metres before reaching the other train, which was stationary. There were no reported injuries, but there was minor damage to signalling equipment and a set of points.