This is from British Pathe news in the 1970s, filmed somewhere in London.
Pretty unique way of mounting those huge, fluorescent lanterns but doesn't seem particularly safe!
Although very unusual these days, in previous times the slinging of lanterns across the roadway was common practice especially where the tram / trolleybus infrastructure was in situ. In addition to this, the use of buildings to anchor the overhead span wires was also far from unique.
Courtesy of Mr Henry Priestley, the following image is of Aberdeen back in 1955. Showing a very busy scene, the inclusion of the new fluorescent streetlighting installation amongst the soon to be dismantled tramway system, makes for an interesting contrast. As has been well documented, the huge wealth of images from our transport heritage is also a great source of reference for the connoisseur of streetlighting.
Referring to the 70s Pathe footage, I would suspect the weight of these lanterns would be well within the capabilities of the catenary cable, although the style of column doesn't suggest it previously had a role in supporting OHLE as used for electric traction. Am I correct in thinking that the canopy of these 5' lanterns would be made out of fibreglass or pressed aluminium sheet?
Interestingly, when tramway traction poles where erected, even with their deep root they were always skewed slightly off the vertical, away from the highway. This was to counter the pull of the OHLE when fully loaded.
As we know, traction poles were also used to support streetlighting, therefore they survived far longer than the original transport system. Once the overhead wires were cut down, the traction poles were free of their loading and for the most part returned to their off centre position.