Interestingly, it would seem that failures of LED lanterns are not just electrically related. From the experiences of one LA, the spigot mountings  can be susceptible to fracture under major stress.
I would suspect this would be down to an impact, although it might also be possible to crack the casting due to high torques applied during installation and final fixing.
Some of the new lantern designs seem to be quite cumbersome in relation to the mounting point, therefore might warrant a strong grip to stay in position on the column. It could therefore be easy to apply too much force, in the belief that the lantern will be more secure (against wind and vibration) as a result.

_________________
"I can't think what you want to go to London for, you won't find any better lampposts there..."
L.S. Lowry. 1887-1976.

In my view, the Stela is horrible and cheap. Where I have seen them,  the street is lit mostly by the car headlights. You can't see at all because the majority of the LEDs have died - you know you have a problem.

Not a single lantern down a street near me has all LEDs still lit and they are only 2 years old. That's awful.

It's still worth bearing in mind that the Stela can be considered the genesis of LED street lighting in the UK. Normally any sort of 'first' just shows off what can be done but from there the technology is further developed (think about cars and buses built in China, 5 years ago they were poor quality.  Whilst I'm not sure about the cars side of thing, on the buses and coaches front one particular brand has the quality and aftercare to rival that of a long-established English brand).


I have an Orangetek TerraLED lantern and for 2 weeks had it in use on a test bracket - the bracket being in the exact same position as on previous tests when using a QSS/QSM lanterns, with the HID lighting the cutoff optics meant the last 1-2m of garden at ground level was not being illuminated, but the TerraLED is providing a few more lumens at this far end of the garden..

The main road closest to me, Malton Road, has seen its QSMs and ZX2s replaced by V-MAXs; they run at 86W compared to 150W lamps in the SON lanterns, and the new illumination is crisp and even along the length of the carriageway compared to the "zebra stripe" effect under the ZX2s and QSMs.

I have counted not more than 3 V-MAXs failed, out of about 150-300 installed, and there have been between 6-10 failed TerraLED lanterns out of between 4,000-6,000 units in use... maybe it's because these run on Philips drivers and not some cheap knockoff unit.

_________________

That makes sense, but when Stelas down side roads work fine, (generally lower voltage) main roads seem to fail miserably, so I would like to see if this is something they've actually rectified or not.

It's not a voltage thing - the LEDs all use the same voltage. It's a heat thing. Larger Stelas use more LEDs which create more waste heat which doesn't seem to be dissipated causing failures - the Stela long is an example.

On another note, side road lighting is lower wattage than main road lighting. Voltage is another matter, as is current. Lower wattage is lower energy. Lower voltage is not.

Just to add another experience to the mix...

Bolton Councils first toy with LED consisted of a few streets fitted with a variety of Stelas in around 2010/2011.
https://goo.gl/maps/maypaiYKGqq


I don't think a single fitting has suffered any sort of total LED failure. I have noticed that the narrow fittings are now seemingly going dimmer and the light is much more lemony yellow than blue/white it originally was. The wide fittings are less affected.

Oops, I meant wattage.

Since the SOX and SON lanterns were replaced along the main roads in my town a couple of years ago there have been multiple failures, you just never (or very rarely) had that number of faults previously.

Watersplash Lane/ Sopwith Road, Bracknell the Road was build in 2015 and by early 2021 atleast two Philips Luma had problems with only some of the LED working. They have since been replaced by smaller Philips Luma.
https://maps.app.goo.gl/fpsVdvSexnK7KPHb6?g_st=ic
Here’s another one in Reading on Forbury Road near the Banksy painting
So you know what I mean. This road was relit to LED in 2017.I saw multiple Lumas that look like that over the years. https://maps.app.goo.gl/xKa9cK8yzg39jpX86?g_st=ic
On M4 junction 7 Huntercombe Spur, the early Indal Lumas from 2012 are now quite deem looking with the LEDs being not as bright as the ones on A4 Bath Road which were installed in 2017. https://maps.app.goo.gl/th4Zx4JkkSyUURvu6?g_st=ic