Last week, a photo tweeted out by the International Space Station went viral, showing the two cities of Baltimore and Washington, DC side-by-side lit up at night under clear skies. Viewers immediately noted how the two cities resembled a pair of twin galaxies in outer space.
Although the two nearby locales appear to be twins, is is apparent that Baltimore appears to be much more white in color while DC is much more orange and yellow in color.
Why is that?
Namely, it is because of a city-wide initiative that Baltimore recently completed. Bmore Bright was dedicated to adding new LED lights and converting all city street lamps to LEDs, which are brighter, cheaper to run and are more energy efficient. The bulbs also last much longer, and the City says they will "reduce maintenance costs by 60%". That area of Baltimore that is still yellow-orange? That's the Seagirt Marine Terminal and Mid-Atlantic Terminal ports, which appear to still be on older lamps.
DC is planning on implementing a similar project, right now only about 5% of the city's lights are LEDs, while the rest are high-pressure sodium high-energy discharge lamps.
Some studies say that the white LED lights, which better represent natural daylight, also reduce crime in areas of cities where they have been implemented. However, there are conflicting sources on whether or not this is actually true.
Source: GGWash.org