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Urbis Opalo 1

Genre: Enclosed Horizontal Traverse High Pressure Sodium Lantern

As soon as the low pressure sodium lamp (LPS) was developed, the race was on to develop a version which would run at high pressure (HPS). The research was stimulated by the prospect of the spectral broadening of the light emitted from such a bulb and the improved colour rendering which would result. However the development was hampered by the lack of a translucent material which could withstand the chemical attack of sodium vapour at extremely high temperatures and pressures.

It wasnít until the early 1960s that General Electric (GE) cracked the problems, closely followed by the GEC and Philips. A prototype high pressure sodium lamp was exhibited at the APLE's annual conference in 1963, but it wasnít until 1966 that the GEC erected an experimental installation along East Lane, Wembley (which, incidentally, also saw the first experimental medium-pressure mercury installation over thirty years before).

The first commercial installation in the UK was erected along the Southend ring road, but it was the City Of London who gained the most recognition by beginning a radial upgrading of all their lighting to high pressure sodium in 1967. As the early HPS bulbs were designed to be retrofitted into existing mercury installations, the lanterns chosen by the City Of London were slightly modified versions of existing mercury lanterns.

The first true HPS lanterns (designed from scratch with the new light source in mind) appeared in the late 1960s and early 1970s. All these lanterns utilised a cross-over design: whilst this was an adaption of existing mercury lanterns, it also moved the lamp up into the lanternís canopy (where it could not be directly viewed by drivers, thus minimalising the glare) and allowed designs to cater for both cut-off and semi-cut-off.

Wider adoption of high pressure sodium was stalled by the energy crisis, as it couldnít match the efficiency of its low pressure sodium brother. Councils, believing in the simple maximum lumens per watt paradigm, replaced existing tungsten, mercury and fluorescent schemes by low pressure sodium. So it wasnít until the 1990s that HPS started appearing in greater quantities.

With its efficiency between high pressure mercury and low pressure sodium, HPS became even more attractive when LPS was finally exorcised from the British Standards of street lighting (as it didn't provide an adequate colour rendering). However, it didn't remain as first choice for new and replacement lighting schemes for long. Renewed interest in fluorescent (from compact fluorescent sources), the emergence of affordable metal halide and the possible introduction of LED have all questioned the automatic selection of high pressure sodium for schemes.

Therefore by the end of the first decade of the new century, high pressure sodiumís position as the natural choice for street lighting was coming under pressure.

Name: Urbis Opalo 1
Date: Circa Late 2000s -
Dimensions: Length: 400mm, Width: 255mm, Height: 210mm
Light Distibution: SealSafe 1640 system. Conforms with BS 5489-1 / EN 13201.
Lamp: 50W, 70W, 100W SON; 70W CDM; 45W, 57W CFL.


The Urbis Opalo first appeared in the mid 2000s as part of the short-lived "Topaz" range, a division designed to offer value for money. As such, it may have been seen as a "cheap" Urbis option, which may account for the Topaz brand being dropped several years later. The Opalo was the only lantern from this range to subsequently appear in the main Urbis catalogue.

The smaller Opalo was launched first with the higher wattage, and larger, Opalo 2 and 3 models arriving shortly afterwards. A classically styled lantern, it conjured up designs from several decades earlier, but with a modern twist.

Far less functional looking than the older ZX range, the lantern included Urbis' commitment to high IP rating and easy maintenance. The lantern was an exercise in space saving with the majority of its internal space taken up by the optical system. The gear was mounted near the spigot mounting which, to save space, only accommodated a side-entry spigot with external top-mounted socket-set screws.


Not surprisingly the Urbis Opalo is proving to be a popular choice and has started appearing in large numbers around the country. The introduction of the Opalo 2 and Opalo 3 has now seen the lantern used for main road lighting.


No external Urbis logos can be found on the lantern (although there's plenty of stickers inside the lantern canopy to positively identify it). But the lantern's classic styling, smaller size and the unique bowl (with its diffuser sections) make it easy to identify. The only other similar lantern is the Thorn Jet which uses the same optical system - this has a higher mounted spigot hole.

Optical System

The Opalo 1 uses the Urbis 1640 reflector which can accommodate lamps up to 100W. This includes options for SON (50W,70W and 100W) , CDM (70W) and CFL (42W and 57W).

The Urbis Opalo 1 In My Collection

facing profile

This lantern was briefly installed in Sussex before being removed and obtained from the lighting engineer. It was in excellent condition having only been in service for short period. It was fitted with a 70W SON-T lamp.

front profile

The lantern has classic styling, being very reminiscent of earlier side-entry mercury lanterns with glass refractor bowls which were popular in the 1960s through to the 1980s.

trailing profile

The lantern has a metal canopy (so complies with the WEEE directive) and a distinctive polycarbonate bowl with a diffused area tilting down towards the back of the bowl. The bowl is held in place by two clips which, when released, give access to the lamp and the control gear. The gasket is fitted to the bowl which can be easily completely removed. Internally the canopy is marked with the Schreder logo (Schreder being the parent company of Urbis) and P15611.


Another novel feature of the lantern are the spigot securing screws which are mounted on top of the canopy and can be tightened to hold the lantern. This design saves extra space as there's no large area at the back of the lantern to accommodate a universal spigot mounting assembly.


The NEMA photocell is fitted as standard. There are no other features on the canopy of the lantern.


The hinges which allow the bowl to open can be clearly seen at the back of the lantern in this view.

pedestrian view

The 1640 reflector can be seen in this view which is responsible for the lantern's lighting distribution. The diffused area at the back not only controls part of the light but also hides the gear compartment at the rear of the lantern.

open bowl

Opening the bowl reveals the gear compartment. This can be pulled out of the lantern so the gear can be easily checked and replaced if necessary.


This view of the opened lantern clearly shows the 1640 reflector, gear compartment and the identification sticker. The full designation of this lantern is the Topaz "OPALO-1/70-HPS/1640/P/NEMA/ELT-BAG/240V/M8x45/NLP."It has an ELT VSI 7/22-3T-GI-P ballast (which was made in Spain), a ICAR Ecofill 12uF capacitor (which was made in Italy) and a BIAIG NI70 S 4K igniter.

Urbis Opalo 1 - During Restoration

An interesting brand new design from Urbis, the Opalo 1 is only just starting to appear on our streets.

The lantern is fitted with 70W SON.

The original location of the lantern is unknown, being obtained by swapping with another collector.