the dark spots that form between poles with sodium lamps strung along residential streets

Across North Carolina, the "greener" streetlights are beginning to appear in pilot studies in Charlotte, Raleigh, LED high bay light and Greenville. In November, Asheville began the third and final phase through Progress Energy Carolinas to upgrade LED streetlights on city-maintained roads.

In Fayetteville, PWC installed the first electric streetlight around 1910 on North Cool Spring Street downtown, and more than 40 were added along Hay Street in 1913.

Today, sodium-vapor-powered lights have been ubiquitous across the city for a generation, casting a yellowish glow over streets and sidewalks. Sodium vapor replaced mercury-vapor lights, which were the industry standard in the 1950s and '60s.
But mercury lamps became an environmental liability, and disposing of burned-out mercury bulbs became costly, said Reggie Wallace, interim chief operating officer for PWC's electric system.

He said streetlights with LED fixtures cast white light that spreads out, reducing the dark spots that form between poles with sodium lamps strung along residential streets.