Car park lighting: height, layout and uniformity
In a car park, the feeling of safety depends more on the uniformity of the light than on installed power. Column height, spacing and motion detection decide the result perceived by users.
6 min read
The car park has eighty spaces and six columns. At six in the evening in November, the aisles are properly lit and the areas between the columns stay dark. That is precisely where the vehicles are parked and where the employees walk.
The reflex is to increase the power of the sources. The real cause is almost always a distribution problem, and it is solved through the layout.
Surface car park, covered car park, company car park
Three configurations are encountered and they do not call for the same answers. A surface car park is lit from columns or from the building façade, with a strong constraint of light spilling towards residents.
A covered or multi-storey car park is treated like a room, with ceiling luminaires, a low clear height and a contrast issue at the entrance and exit. The surfaces there are often dark and absorb a large share of the flux.
A company car park adds a regulatory dimension. It is both a traffic route and a workplace for the people who work in it. The French Labour Code, in article R4223-4, sets minimums of 10 lux for outdoor traffic routes and 40 lux for outdoor areas where permanent work is carried out.
Column height and spacing between light points
The mounting height determines the area covered by each light point. The higher the luminaire, the wider the area it covers, and the more the beam has to be narrowed so as not to light beyond the site.
| Mounting height | Suitable use | Point to watch |
| --- | --- | --- |
| 3 to 4 metres | Pedestrian paths, small parking pockets | Exposure to vandalism |
| 5 to 6 metres | Standard surface car park | Column spacing |
| 8 metres and above | Large areas, HGV manoeuvring areas | Light spill and glare |
A proportion rule serves as a first approach: the spacing between two columns is commonly between three and four times the mounting height, depending on the photometry chosen. This order of magnitude is used to sketch a layout, it does not replace the calculation.
The position of the columns is then aligned with the parking plan. A column placed at the head of a bay, between two rows of spaces, lights twice as much useful area as a column aligned along the edge of the site.
Uniformity: why it matters more than the average level
Uniformity U0 is the ratio of minimum illuminance to average illuminance. A car park with an average of 20 lux but with dips down to 2 lux is perceived as poorly lit, because the eye adapts to the brightest point and can no longer make anything out in the dark areas.
The EN 12464-2 standard, which covers outdoor workplaces, sets graduated levels for parking areas according to traffic intensity, with an associated minimum uniformity. The usual reference values are 5 lux for light traffic, 10 lux for medium traffic and 20 lux for heavy traffic, with a uniformity U0 of at least 0.25.
The calculation is made on a grid covering the whole site, aisles and spaces included. A photometric study of the parking area renders this grid in false colours and immediately shows the dips between columns.
Limiting light spill towards residents
A car park rarely lights only its own footprint. Intrusive light towards neighbouring homes is the main source of complaints, and the flux sent towards the sky is regulated.
The French order of 27 December 2018 on the prevention of light pollution regulates several parameters. The proportion of flux emitted above the horizontal is capped, with a value of 4 per cent for ordinary lighting and a stricter requirement in protected natural areas. The colour temperature of the sources is capped at 3000 kelvins, with lower thresholds in sensitive areas.
The text also sets times. For car parks serving a place of activity, switch-off takes place no later than two hours after the end of the activity, and switch-on no earlier than one hour before it resumes. These times are programmed in the cabinet and documented.
On the equipment side, two features make compliance easier: a flat-glass luminaire, which emits nothing above the horizontal, and an asymmetric optic that keeps the flux inside the site. Outdoor and street lighting luminaires come in several photometric classes for this use.
Motion detection and night-time dimming
A company car park is empty for much of the night. Two devices combine usefully: programmed power reduction and motion detection.
Programmed reduction follows a time profile controlled by an astronomical clock, which automatically adjusts switching to sunrise and sunset. The reduced level must remain consistent with any CCTV requirements, a subject to be dealt with together with the security manager before programming.
Detection raises the level when a vehicle or pedestrian approaches. Three settings determine whether it is accepted: the range, the time delay before returning to the low level and the standby level. Too slow a rise leaves the pedestrian walking in the dark, too short a delay causes switch-offs in the middle of a manoeuvre.
Control can be built into the luminaire or centralised in the cabinet. Control and detection devices are chosen together with the luminaires in order to guarantee driver compatibility.
Vandal resistance and impact rating
Two ratings are read on the data sheet. The IP rating describes ingress protection: the first digit concerns solid bodies and dust, the second water. For an outdoor luminaire exposed to driving rain and cleaning, IP66 is the usual benchmark.
The IK rating describes resistance to mechanical impacts. IK08 corresponds to an impact energy of 5 joules, IK10 to 20 joules. The level required depends directly on the mounting height: a luminaire within reach from the ground needs a high IK rating, a luminaire at 8 metres much less.
Three other points count in an exposed environment: stainless steel or tamper-proof screws, a body in aluminium or UV-resistant polycarbonate, and an access hatch requiring a special tool. Class II electrical insulation also avoids having to redo an earth connection on old columns.
Connection and takeover of an existing installation
In an existing car park, the luminaire is rarely the most demanding item. The preliminary inventory covers four elements: the condition of the columns and their foundations, the condition of the buried cables, the compliance of the control cabinet and the presence of a usable earth.
Corrosion at the base of a column is checked by local stripping, at the point where it is embedded in the foundation, where water stagnates. A column corroded at this level is not reused, whatever its appearance higher up. The weight and wind surface of the new luminaire must also remain compatible with the original design calculation of the support.
The mounting plate is the last compatibility point. Brackets and column tops come in several diameters, and the adapter must be ordered with the luminaire. Examples of parking area renovations show how these constraints are dealt with at survey stage rather than at installation stage.
Floodlights and luminaires for parking areas are grouped in the car parks category, completed by outdoor LED floodlights.
