up to the home signal of the next signal box and the section signal cannot be cleared In an emergency, and then only when authorised by the signal box supervisor or Operations Control, so that a train carrying passengers can enter an occupied section to use a station platform An engineering train is to move towards a possession, or leave a line under possession at an intermediate point A train is to pass the signal protecting engineering work to gain access to a station where the train is required to start back, or a line under single line working, or a siding The line is to be examined to check that it is clear A train is to proceed at caution through an absolute block section from the signal box in rear when a failed train has been removed A train is to enter the section after a train or vehicle that has proceeded without authority has been removed, or the front portion of a divided train has passed through the section A train is to enter the section to assist a failed train, evacuate passengers from a failed train, remove a portion of a divided train, or remove a train or vehicles that have proceeded without authority Single line working applies Working by pilotman or modified working applies The driver and signaller must come to a clear understanding, and ensure they agree about how it is to be done. In the UK the signaller tells the driver of a specific train to pass a specific signal at danger, proceed with caution and travel at a speed that enables him to stop short of any obstruction, and then obey all other signals. If the signal is fitted with TPWS, the driver resets the Driver Reminder Appliance, pushes the TPWS Trainstop Override button in the cab, and proceeds cautiously through the section. If the train reaches the next signal without finding an obstruction, they must obey its aspect, at which point they can revert to normal working. Driver passes a signal at danger under his own authority If contact with the signaller cannot be made then the driver must not move the train, unless it is standing at one of the following signals: An Intermediate Block Home signal A signal controlled from a signal box that is closed An automatic signal where local instructions permit it, e.g. signals within tunnels on