I think it's a shame sodium vapor lamps are being replaced. Low pressure sodium (LPS) is actually highly efficient, provide a very soothing color for nighttime, and for me most importantly are easily filtered by astronomical observations (their spectrum is nearly a single line). Their size and unwieldiness is justified in utility street lightning setting.

http://adsbit.harvard.edu/cgi-bin/nph-iarticle_query?2001IAU...