Control points can vary greatly in complexity depending on the size of the interlocking they serve. A simple control point may manage only a few switches and signals, while a large control point may control many routes, signals, switches, track circuits, and communication systems.
One major factor is the number of switches and signals. The more equipment that must be controlled, the more complex the control logic, wiring, indications, testing, and operator interface become.
Track layout also affects complexity. Junctions, crossings, sidings, yards, crossovers, and multiple routes create more possible movements and more potential conflicts that must be protected by the interlocking system.
Automation also increases complexity. Manual systems may rely more on operator actions, while automated systems use computer controls, software logic, diagnostics, event logs, and communication networks.
Additional features such as speed control, route setting displays, remote control, alarms, diagnostics, and data recording can also increase the complexity of a control point.
The more complex the control point becomes, the more important proper design, testing, documentation, training, and maintenance become. Larger control points may also require more operators or additional support systems to manage train movements safely.