Post-top luminaire or street luminaire: the difference and where to use each

The difference is in the mounting

A post-top luminaire slides over the top of the column. The column ends in a 60 to 80 mm spigot, the luminaire clamps onto it with clamping screws and the light source sits directly above the column. A street luminaire has a side entry: you slide it onto a bracket arm or tilt it on the column top, so that the light source hangs above the carriageway or path rather than above the column.

That single difference determines the shape of the luminaire, the light distribution, the column height and how the street looks by day. Both types in our range are IP66, carry a 5 year warranty and fit the same steel columns from TURRIS or aluminium columns from CIVIS.

Light distribution: all round or along the road

A post-top luminaire distributes the light symmetrically around the column. The modern symmetrical version from POLARIS has a 90 degree beam and puts a circular pool of light on the ground roughly two to three times the mounting height across. At 4 metres that is a circle of 8 to 12 metres. The light therefore also falls on verges, lawns and facades next to the path. That is exactly what you want on a square or in a park, and exactly what you do not want along a road with gardens beside it.

A street luminaire uses an asymmetrical optic, usually described as Type II or Type III. Type II throws a narrow, elongated beam along the road and suits paths and streets up to about 1.75 times the mounting height wide. Type III reaches wider, up to about 2.75 times the height, and suits wider streets and car parks. The columns can therefore stand further apart. As a rule of thumb, allow 3 to 4 times the mounting height with a post-top luminaire and 5 to 7 times with a street luminaire with road optic. At 4 metres that is 12 to 16 metres against 20 to 30 metres.

In practice this means:

• fewer columns per 100 metres of road with a street luminaire, so less trenching and fewer column cut-outs
• less spill light onto facades and bedrooms with a street luminaire
• a more even picture on squares, in parks and on parking areas between buildings with a post-top luminaire

Atmosphere or function

In residential areas, parks, cemeteries and around an office entrance, what matters is how the column looks by day and how warm the light is. A post-top luminaire belongs there, modern or classic, preferably in warm white from 2200 K to 3000 K. With the modern POLARIS you set wattage and colour temperature after installation with a remote control, so you can go to 3000 K or 2200 K on site if residents ask for it.

On business parks, distributor roads, car parks and cycle paths the issue is lighting class, uniformity and energy per metre of road. That calls for a street luminaire with a directed optic, usually in 3000 K or 4000 K, with a dimming profile via dip switch, 1-10V, DALI-2 or D4i. The street luminaires from VIA come with 10 kV surge protection as standard, not a luxury on long cable runs outside built-up areas.

The P classes from EN 13201 for pedestrian areas and paths give guidance: broadly, P4 requires an average of 5 lux, P3 7.5 lux, P2 10 lux and P1 15 lux, with a minimum of roughly one fifth of the average. Which class applies is set by the road authority or the client; a residential path is often P4 or P3, a business park or car park P2 or P1. The higher the class, the sooner a directed street luminaire on a taller column beats a post-top luminaire.

Column height and spigot diameter

Post-top luminaires usually sit at 3 to 4 metres, rarely higher than 5 metres. Any higher and an all-round luminaire becomes too weak at the edge of its pool of light, or you have to raise the wattage so far that glare increases. Street luminaires sit at 4 to 6 metres in residential areas and on business parks, and at 8 metres and above along main roads.

Mind the spigot diameter at the top. The VIA street luminaires fit a 60 mm spigot and tilt, so you can mount them on a bracket arm or directly on the column top. The POLARIS post-top luminaires fit 60 to 80 mm; the classic version needs 80 mm. Order the column cut-out from NEXUS at the same time: it fits in the door opening and takes care of fuse, lampholder and earth braid in one go.

Examples from POLARIS and VIA

Four worked examples with articles from our range:

• Residential path or courtyard, post-top at 4 metres: POLARIS symmetrical, 30 to 60 W adjustable, 9,600 lm at full power, 90 degree beam. Set to 30 W and 3000 K this gives a warm, all-round lit scene with columns every 12 to 16 metres as a rule of thumb.
• Park or square with a classic look: POLARIS classic 40 W, 4,000 lm, 4000 K, 120 degree beam, on an 80 mm column. Here the shape of the luminaire by day weighs as much as the light after dusk.
• Cycle path or residential street, street luminaire at 4 metres: VIA 25 W, 1,500 lm, Type II Short optic, matched to a mounting height of 4 metres. Low wattage, little spill light, impact rated to IK08.
• Distributor road or business park at 6 metres: VIA 20 to 50 W adjustable, 6,750 lm, Type II optic, or the version up to 40 W with a separate driver (for example AstroDIM 1-10V), or the DALI-2 version up to 40 W with D4i, so you choose the control yourself.

All luminaires mentioned are IP66 with a 5 year warranty, from European stock within 5 working days; steel columns in 3 to 5 weeks, aluminium columns in 4 to 6 weeks. Lichtplein supplies businesses only, prices exclude VAT.

Decision aid in four questions

If in doubt, run through these questions:

• Is the light point above a road or above an area? Road: street luminaire. Area, such as a square, park or parking area between buildings: post-top.
• Are there homes or gardens right next to the light point? Then preferably a street luminaire with a directed optic, or a post-top at low wattage in 2200 K to 3000 K.
• Which lighting class has been agreed? From P2 or an M class for carriageways: usually a street luminaire at 6 metres or higher.
• Does the luminaire have to look good by day? Then post-top, modern or classic, and choose the column to match.

Frequently asked questions