What is true of permanently illuminated signs?

Permanently illuminated signs are used to manage traffic flow and safety on the road. They serve specific purposes based on their indications.

1. Permanently illuminated signs that either block lanes or open them up to traffic help guide drivers on which lanes are safe to use or which are closed. This is crucial for maintaining orderly traffic and preventing accidents.

2. The prohibition against stopping at the side of carriageways when illuminated indicates that drivers must continue moving rather than halting in potentially dangerous areas. This helps maintain traffic flow and ensures safety.

The incorrect option stating that these signs apply only to multi-track motor vehicles is not relevant. Permanently illuminated signs are applicable to all vehicles on the road, not just specific types.

Understanding the combination of choices ensures compliance with traffic regulations and enhances road safety for everyone.