How is the lighting technology selected?

By working through a few decisions in order: whether life and power or price and simplicity matter most, what the change does to the series circuit and CCR, what the climate and vision systems need, and how the lights will be maintained. The result is checked against the photometric requirement and the manufacturer’s data.

An LED fixture has a long life, low power and colour made directly by the LED, and the routine lamp change largely disappears. A halogen fixture is simple, cheaper to buy and well understood, but its filament wears out and runs hot. Both must meet the same photometric requirements on the same series circuit.

The load becomes lighter and is driver electronics rather than a simple resistive load. The series circuit load and power factor should be recalculated, because a lighter load can change CCR loading and regulation. The circuit must stay within the CCR’s minimum and maximum load limits, and the fixtures must follow every brightness step of the CCR with correct output at each and no visible flicker, particularly on a thyristor CCR.

A halogen lamp’s waste heat helps keep inset lenses clear of snow and ice, and LEDs give little heat at the lens, so heating options and the snow-clearing method need checking. LEDs also emit little infrared, so cameras and enhanced vision systems must be confirmed to still see the lights.

That the fixture meets the required intensity, colour and beam pattern at every step, that the circuit load, power factor and CCR regulation are acceptable, that snow clearing and vision systems are covered, that driver and module spares are planned, and that the whole-life cost has been compared. The manufacturer’s data and the standard decide.