Philips MA 50 (MA50 135XDS00*1)
Genre: Enclosed Horizontal Traverse Low Pressure Sodium Lantern
The low pressure sodium discharge lamp was developed by Philips in 1932. After two successful trial installations
(including the first low pressure sodium installation in the UK along the Purley Way, Croydon) the first commercial installation
was installed by Liverpool Council in 1933 using specially commissioned lanterns from Wardle.
The development of lanterns continued through the 1930s and accelerated when it was determined that the lamp’s brightness and
its long length made it less susceptible to glare. Lanterns with bare bulbs suspended over an overhead reflector (the so-called "seagull" lanterns)
quickly followed. Glass manufacturers were initially slow as the first plate refractors for low pressure sodium lamps didn’t appear
until the end of the decade.
The advantages and disadvantages of low pressure sodium were readily debated, especially when an alternative (the medium and high
pressure mercury discharge lamp) was also available. The monochromatic light was considered especially useful for arterial
and traffic routes, the lamp’s shape cast a wide beam across the road surface, the light was also considered more penetrating
in foggy conditions and it was the most efficient light source being manufactured. However, the light was also considered
inappropriate for high streets, promenades, civic areas and residential streets and so some lighting engineers
restricted its use to traffic routes only. Therefore low pressure sodium became known as "the drivers’ lamp."
The arrival of plate glass refractors resulted in large lanterns made of metal frames enclosing heavy glass sheets.
These bulky lanterns continued to be made into the 1950s until being usurped by lanterns with plastic bowls and
machined or moulded plastic refractor plates. The lanterns were still large; the size dictated by the bulky
control gear, but their design and construction was becoming simpler.
The 1950s and 1960s saw huge improvements in the construction and efficacy of low pressure sodium. Early two-piece
designs (dubbed SO) were replaced by the one-piece, more efficient integral design (called the SOI). The development of
linear sodium (SLI) broke the one hundred lumens per watt barrier, lead to a radical rewriting of the British Standards
of street lighting and prompted the development of new families of streamlined lanterns. But it wasn’t until the arrival
of a new heat-reflecting technology (called SOX) that a cheap family of extremely efficient bulbs became available.
The energy crisis of the 1970s saw a rethink in street lighting and lamp efficiency became dominant when fuel was both
in short supply and expensive. This saw the large scale removal of colour corrected high pressure mercury, fluorescent and
ancient tungsten lamps by low pressure sodium replacements. The old arguments that the smoky-orange lamps were inappropriate
for residential areas no longer applied. By the end of the 1980s, low pressure sodium was the dominant street lighting lamp used in the UK.
The use of low pressure sodium came under scrutiny again. High pressure sodium, finally developed as a viable technology in the
1960s, was coming of age and offered a compromise of slightly less efficacy with better colour rendering. Questions were
being asked about the physiology of the eye and visual adaptation under low lighting levels; previously the wavelength
of low pressure sodium had been deemed the most suitable, but research now suggested that the eye responded better to white
light. Concerns were raised about light pollution and the low pressure sodium lamp was seen to be the chief culprit
(although it was more to do with older non-cutoff and semi-cutoff optical designs rather than the lamp itself).
By the turn of the century, the age of low pressure sodium was seen as coming to an end. Research in white light technologies,
especially metal halide and a renewed interest in compact fluorescent coupled with the advantages of using white light at
low lighting levels, saw the end of the low pressure sodium lamp’s dominance. Its use was discouraged in the specifications,
lantern manufacturers started to wind down their production and bulb manufacturers followed suit.
By the end of the first decade of the 2000s, low pressure sodium was in stark decline, and less and less of the UK’s
streets were being lit by its characteristic orange glow.
Name: Philips MA 50 (MA50 135XDS00*1)
Date: Mid 1970s - Mid 2010s
Dimensions: 1066mm, Width: 270mm, Height: 180mm
Light Distibution: Semi Cut-Off and Cut-Off (BS 1788:1964, BS 4533:1976)
Lamp: 135W SOX
The 1970s saw increased competition amongst the UK's main road street lighting as companies vied to tender
for the lucrative new motorway contracts. The main players, the GEC, Thorn and ELECO, all
pushed their lanterns, and made claims for their luminaries to be the 'first' or to have been used for the 'largest' contracts
on a new motorway scheme.
Another player entered the arena when Philips joined the fray. The Dutch company had been instrumental in
the introduction and sale of Low Pressure Sodium (LPS) lamps since the 1930s. However, the firm never produced UK
specific luminaries, preferring to pair up with other manufacturers for advertising, marketing and sales.
This led to some UK manufactured lanterns being rebadged as Philips products – the main road lighting GoldenRay
lighting range from ELECO being a well-known example, as it was sold by Philips as the MA 5, MA 6
and MA 9.
This changed in the early 1970s with Philips introducing the MO5 "Links" Lantern, a design specifically
catered for the major motorway construction at the time. Spurred on by its success, the firm decided to fully enter
the UK market for itself, designing luminaires which would meet British and European Standards, but which would
have several new features. The Links lantern was joined by the MO62 "Catenery" Lantern, and the firm
started boasting their own 'firsts' in multiple-page glossy advertising features.
Seeing further opportunities with the expansion of the UK's motorway network, and the re-lighting programs spurred on
by the energy crisis, Philips embarked on an even bigger venture, and designed a new range of LPS and HPS lanterns
for the UK market. Noting that competition was fierce, particularly with the established players, Philips knew that
their new main road LPS luminaries would have to stand out from the crowd.
Starting with existing European designs (such as the Philips SDS 252, SRM 120 and SRM 120/X), the
firm created new design which had several unique characteristics: it was modular; it had changeable optics; gear was housed
in a separate module; it cut down on spares stock; it was easily serviced with parts being easily replaced; and the final
design was polished off by leading Industrial Designers (Tony Butowsky and B. Rogers). In short, it was so
revolutionary, Philips didn't even feel the need to give it a name in their catalogues and advertising – it was just
the "MA" and that was the end of it.
The first adverts appeared in multiple page spreads in 1975. The modular family of lanterns, comprising 90W, 135W and 180W
versions, was made of three main modules: a GRP canopy, prismatic acrylic bowl and shoe (which could optionally be fitted
with gear). Optical characteristics could be changed from semi-cut-off (the major system used in the UK) to cut-off by
simply repositioning the lamp. And being based on LPS, the lantern could also boast its energy efficient credentials,
being based on the most efficient light source at the time. In short, it was a winner.
Uptake was brisk. It was used in the new motorway schemes and dual carriageways during the 1970s, and started to be
used for major traffic routes, arterial schemes and dual carriageways in the 1980s. By the 1990s, it has also established
itself as the replacement lantern of choice, with the smaller 90W model being used in many towns and cities. It probably
became the most popular LPS luminaire in the UK for lighting main roads.
Changes over its lifetime were minimal. The minimal gearless shoe, which was just a design embellishment, was joined
by a brute, functional spigot, which changed the lantern's flowing lines, and was obviously a nod to budgetary constraints
than design. Gear was also moved into the lantern's canopy itself; this made servicing easier but again ruined the appearance
of the lantern. And a fifth clip was added to the tip of the canopy, probably the result of experience, and a requirement
to prevent dust, water and insect ingress.
It was a dominant force in the lighting industry for decades. But its demise was not due to a superior model or
better design, but another revolutionary change in the industry. Most were lost to LEDification in the 2010s, as huge
replacement schemes saw the lantern replaced in swaths by LED. But these lanterns, rightfully awarded an
Industrial Design Award winner in 1975, showed that given an opportunity, the right design team, and an exemplary
design, could be dominant on the UK's road for over forty years.
The lantern was firstly used widely on the UK's motorway network in the mid to late 1970s
with general main-road usage following in the 1980s. Gradually it became almost ubiquitous, with it
being used for all new schemes, and as a casual replacement for most existing installations. It became
the most popular UK luminaire for main road use.
It was a unique looking lantern, thanks to its slim profile, wide housing, white canopy and distinctive
shallow refractor bowl. Gear and shoe options only changed the appearance of the spigot mounting and were
The primary optical system was the wide, shallow refractor bowl which provided a semi cut-off distribution
in accordance with BS 4533 (1976). The white canopy of the luminaire acted as a secondary optical system,
reflecting light emitted above the horizontal back towards the bowl. Repositioning the lamp holder and lamp support
changed the optics to cut-off (again, complying with BS 4533).
The gear was housed in an optional gear shoe which could be separately fitted to the luminaire. It was easily
accessible and easily replaced. Later designs of the luminaire housed the gear in the main body of the lantern
where it could be accessed by opening the bowl.
Philips MA 50 In My Collection
The provenance of this lantern has been lost to the mysts of time. It was obtained in the early 2000s from fellow collector
The width of the lantern, its shallow depth and its unique bowl refractor pattern can be clearly seen here.
It differs substantially in dimensions from earlier LPS designs, which were much narrower and deeper
than this luminaire.
The luminaire was made from three basic modules: the white GRP canopy, the acrylic refractor bowl and the small,
functional gear shoe. This version is fitted with the most basic shoe, which is just a minimal, reinforced spigot.
(This option wasn't available originally in the 1970s and appeared later in the luminaire's lifetime).
The lantern's plain smooth canopy is typical of early 1970s design when moulded and flowing plastic designs became popular.
Two of the four stainless steel toggle clips can also be seen here; two release the bowl whilst the opposite two function
as hinges. The hinge toggles can be entirely removed themselves allowing easy replacement of the bowl.
The Philips logo is clearly cast into the GRP plastic canopy. The shot also shows how the shoe is
bolted to the canopy, being fitted in like a dovetail rather than fitted flat. All shoes and canopies had the
same configuration, so the shoe could be used with the 90W, 135W and 180W canopies. This truly modular design allowed
the number of spares to be reduced at stock yards, another selling point of the lantern.
The lantern was fitted with a NEMA photocell which was a factory option. (The blue photocell came from several I rescued
The unique refractor pattern is visible in the shot. Whilst this appeared to be totally unique for an LPS based lantern,
it reminded me of earlier HPMV luminaires, such as the GEC Dioptrion. The refractors below the lantern
act as spreaders (thus reducing and smoothing the illumination beneath the lantern, preventing the appearance of 'hot spots' on
the road surface, and avoiding the grooves and white paint used by other manufacturers). The pattern continued around
the lantern, now forming the main beams, which were part of the semi cut-off and cut-off optical distributions created
by the refractors.
The interior of the lantern is extremely simple and plain. The white interior is largely smooth
and there are no extra lugs and holes for additional features. All these lanterns include an identification
sticker, which can be seen just below the lampholder.
All lanterns had to have a sticker or identification plate if they conformed with BS 1788:1964. This sticker shows an
older catalogue number (MA 50 - 00*1/S), Ingress Protection (IP 54) and the two lamp positions: Position One for Cut Off and
Position Three for Semi-Cut Off.
Philips MA 50 As Aquired
Probably the most popular family of SOX lanterns ever.
This is the 135W SOX version, the simplest option, being just the lantern without internal gear or gear shoe.
It was obtained from fellow collector Tim Luckett.