Chances are the pre-1980s lamps were mercury-vapour, not incandescent. Incandescent lamps were obsolete for road lighting by the 1950s. Sodium lamps caught on b

Chances are the pre-1980s lamps were mercury-vapour, not incandescent. Incandescent lamps were obsolete for road lighting by the 1950s. Sodium lamps caught on because they were much more efficient than both.