The reference number indicates the maximum light intensity of a lamp. This number is determined by the light intensity (candela) and has no unit because it is a dimensionless value.

It is widely used in floodlights and high beams to compare light output. Each driving light on a truck has an associated reference value so that it can be checked whether it falls within the standards.

Meaning of high or low reference number

  • low reference numberThese lamps have a wide light beam that does not reach far. They are ideal for use on winding roads or routes with many curves.
  • high reference number:These lamps shine farther and are therefore suitable for long, straight stretches of road.

sum of reference numbers

When you have two lamps, for example, each with a reference number of 17.5, the total reference value on the vehicle is 35. It is important to check what the legal limits are for the total reference value of high beam on vehicles in your country. In some countries, the total value, for example, must not exceed 100.

It is crucial to consider the application of the lighting and the environment in which you are driving. For winding roads, a lower reference value is better for broader illumination, while for long, straight stretches, a higher reference value provides further visibility.

Relevant articles: ECE approval (this specifies which number is allowed in which situation).