Tunnel interior light: evenness, dust and access
Past the transition the eye is settled and the requirement drops to a base level that has to hold evenly along the bore. Here the problems are the wall finish, the dirt and the fact that nobody wants to close a lane.
Specification
What the sheet states for this build, and what is confirmed per project.
| Topic | What the sheet states |
|---|---|
| Zone | Interior, at the base level for the design speed |
| Level | From the calculation, at the maintenance factor |
| Uniformity | Along the bore and across the road surface |
| Optic | Symmetric or wide asymmetric, per mounting line |
| Wall finish | Reflectance, which changes the result at the same output |
| Sealing | Gasket and lens, replaceable in a lane closure |
| Driver | Position and access, side or top of the bore |
| Control | Stepped with the threshold, and dimmable at night |
| Data sheet | Current revision, naming the delivered model |
A light coloured wall lining raises the level on the road for the same output. That is a civil decision, and it is worth raising while the lining is still a choice.
The wall is part of the optical system
Light leaves a luminaire, hits the road, hits the wall and comes back. A dark, rough lining absorbs it; a light, smooth one returns it. The difference shows in the uniformity along the bore, which is why the lining specification appears in tunnel lighting designs and rarely in the fixture data.
If the lining is being replaced as part of the works, model the lighting with the new reflectance. If it is not, model it as it is, dirt included. A design based on a clean white lining in a bore that will stay grey is a design that will not hold.
- The lining material and its reflectance, as it will be maintained.
- Whether the lining is part of the works.
- The cleaning regime for the lining, not just the luminaires.
Symmetric or asymmetric
A symmetric optic puts light on both walls and the road, which suits a bore with light linings and a central mounting line. An asymmetric optic aims across the road from one side, which suits a bore where the luminaires sit on one wall.
Both work; they work differently. The choice follows the mounting line and the lining, and it should be made with the calculation in front of the designer rather than from a preference.
- The mounting line available on each side.
- The lining on each side, if they differ.
- The uniformity along the bore between luminaire positions.
Maintenance in a lane closure
The interior zone is where most of the luminaires are, and therefore where most of the maintenance happens. A fixture that needs two people and a platform costs more over fifteen years than a fixture that needs one person and a ladder, whatever the unit price.
The practical specification is a replaceable driver, a gasket that comes as a part, and a connector that does not need re-terminating. Ask for those three as line items, and ask how long a swap is expected to take.
- Driver position and whether it can be swapped live.
- Gasket and lens as spare parts, with a part number.
- The expected time for one swap, in the closure window.
Before the order
- Lining reflectance in the model, as maintained rather than as new.
- Mounting line agreed, because it decides the optic.
- Spare parts with part numbers, for the closure window.
- Build
- Tunnel interior light
- Line
- Tunnel lights
- Ask for
- Specification sheet, photometric file, aiming drawing
Send the space, get the sheet.
Build, specification sheet and the option list for each line item, in one reply.