A collection of track links together form a network. The network may react to link events as each event occurs or later in time. The network may include slack links which can take up the impact of movement events on filled links. Slack links can be distributed or created via the schedule or dispatcher orders in order to damp development of delays or bottlenecks. Traffic Conditions are interactions with the schedule and operating constraints.
Bottlenecks are the result of the physical constraints of the track, interacting with schedule.
Backed Up Auto Traffic at a crossing The railroad context is traditionally the adjacent landscape and landuse or it could be weather fronts moving in time. The Journey is certainly an object which must be highlighted. Train blocks which contain the train and the safety space in front are a common approach which should be modelled. Traffic flow, decision points and events, scheduled and unscheduled, even thought they may be loosely coupled to physical objects are an important part of any audit of the quality of service. Communication event objects , either the result of human voice or digital device transmission should be modelled and visualized as a way of fleshing out what really happens to make things go the way they do.