What do stop bars consist of?

Stop bars are designed to indicate where vehicles must stop in relation to runways or taxiways, enhancing safety on the airside of an airport. The correct understanding of stop bars is that they consist of a single row of red inset lights. This specific color and configuration serve to effectively alert vehicle operators of the need to stop, particularly at critical points where they may come into conflict with aircraft movement.

The use of red lights is universally recognized as a signal to stop, which helps prevent potential accidents by ensuring that vehicles remain halted at the designated stopping point. Other options involve different color lights or configurations that do not convey the stop signal, thereby failing to serve the primary function of ensuring safety in active airside operations.