Come in two flavours: Low Pressure, which look orange and are a very narrow spectrum indeed. These are actually very efficient, much like LEDs, expect unlikely LEDs they're not available (because it can't be done at that frequency?) coated with a phosphor that re-emits on a broader, almost white spectrum. These give the classic street light look, which is almost black and white - your eyes can't make out colours with this little information and, very positively, your body isn't tricked into thinking it's day time because there is no blue in there spectrum.
High Pressure sodium is more expensive and similar to other arc lamps - a bluish white. Also pretty efficient in terms of lumens / watt.
As a cyclist in Birmingham, all I really want is for the council to fix the sodding pot holes: serving round them puts me in the way of things and they're easily big enough to have me off my bike