This paper is intended to open the dialogue regarding the applications of Next Stage information and work towards a multi-stakeholder consensus on its future use. The ‘Next Stage’ study addresses a long-standing limitation within UK traffic signal
control systems: the inability to accurately identify the next running stage until the controller returns a stage confirmation reply (Gn). This creates a period of uncertainty during interstage, particularly where demand-dependent stages are configured, which
reduces the ability of Urban Traffic Control (UTC) systems and traffic signal optimisers to accurately model junction behaviour and make forward-looking optimisation
decisions.
This paper presents a pilot study undertaken by Transport for London (TfL) to investigate whether existing traffic signal controller functionality can be used to provide advance indication of the next stage before stage confirmation occurs. The study focused on
using the controller’s internal Next Stage (NXTSTG) parameter, which reports the stage the controller is moving towards during interstage. By trialling the transmission of this information through existing controller functionality and standard communications
infrastructure, it was possible to make upcoming stage information available within a UTC instation without additional hardware and with only minimal controller software configuration changes.