A special stage test (GLP) is a special test in vintage car rallies where the aim is not to achieve the fastest time, but to maintain a specified driving time or average speed as consistently and precisely as possible. Participants must complete a certain distance in a precisely defined time. Any deviation from this target - whether too early or too late - is penalized with penalty points.

Measurement with light barriers

For precise time measurement in a GLP, light barriers are often used. These consist of a transmitter and a receiver that create an invisible light barrier (usually infrared). When a vehicle passes through this light barrier, the light signal is interrupted and the exact time of passage is recorded by a timing system.

Light barriers enable very precise measurements down to thousandths of a second, which is particularly important for uniformity tests. The recorded times are then compared with the specified target time in order to calculate deviations and penalty points.

Typical applications in a GLP

1. Start/finish measurement: The light barrier registers the exact start time and the time of the finish passage.
2. Intermediate time measurement: On long tests, light barriers at intermediate points can check that the uniformity is maintained.
3. Secret time measurements: To prevent manipulation, light barriers can be set up at unannounced points.

The high precision of the light barrier measurement ensures that the evaluation is fair and comprehensible.