Street lights that emit narrow spectral lines are not a problem at all for spectroscopy, except of course at the line wavelengths. I have a bit of experience here -- a few more than 400 nights observing spectroscopically at Lick Observatory, where we have just a wee bit of light pollution!
All lights, narrow or broad band, present problems for optical broad band imaging.
If we could get all cities to go with low pressure sodium lamps (that only emit at a few wavelengths), astronomers would be very happy. The only problem is that city residents tend to not like the monochromatic look you get from not having a broadband light source. So San Diego, for example, switched to low pressure sodium in the 80's to try to protect the skies for Mt. Palomar. But residents started screaming (it's leading to more crime!) so the city went back to high pressure sodium.
All lights, narrow or broad band, present problems for optical broad band imaging.
If we could get all cities to go with low pressure sodium lamps (that only emit at a few wavelengths), astronomers would be very happy. The only problem is that city residents tend to not like the monochromatic look you get from not having a broadband light source. So San Diego, for example, switched to low pressure sodium in the 80's to try to protect the skies for Mt. Palomar. But residents started screaming (it's leading to more crime!) so the city went back to high pressure sodium.