As the days grow darker, New Yorkers will begin seeing the city in a new light.

Nearly 72 percent of the city’s 250,000 street lamps have undergone a conversion from old, sodium vapor bulbs — known for their orange glow — to LED bulbs, which have a brighter, whiter glow, according to the city’s Department of Transportation.

The city is on target to upgrade the rest of its lights, which do not include those on highways operated by the state, by the end of 2018.

The bulbs last longer than the old lights and use half the energy, allowing for millions of dollars in savings. Experts say the upgrades promote a sense of safety and security that can inspire New Yorkers and visitors to explore more streets at night.

“There are some cities in the country that close after 5 p.m. New York is not this way and shouldn’t be,” said Harold Takooshian, a professor of psychology and urban studies at Fordham University who has studied the ways streetlights affect neighborhoods.

Mayor Michael Bloomberg approved the plan to upgrade the streetlights in 2013. The first phase began two years later in Brooklyn, followed by Queens in 2016. Nearly 154,000 LED lamps have been installed in the two boroughs to date, according to the latest DOT data. About 25,000 LED lights have been installed in the Bronx, Staten Island and Manhattan.

Overall crime is down 8 percent in the past two years, according to NYPD statistics. It’s hard to make a direct correlation between improved lighting and lower crime rates, Takooshian said, but “it makes people more secure.”

Takooshian said the city has long sought to find ways to better light streets economically and efficiently, in a fashion acceptable for communities.

When they were first installed in 2015, some Brooklyn residents complained they were too bright and disrupted their sleep. Mayor Bill de Blasio and the DOT responded to those complaints and took swift action, the agency said.

“DOT surveyed lighting in those neighborhoods and met with the LED fixture manufacturer, who was able to make a change to a lower wattage (to 72 watts from 78 watts) and switch to a different light fixture that changes the spread of the light,” a DOT spokeswoman said.

The adaptations seem to have worked — elected officials and community leaders say they have not received major complaints about the lights in more than a year.

“To a lot of people this is the norm right now,” said Jeremy Laufer, district manager of Brooklyn Community Board 7.

Los Angeles, Oahu and Phoenix are planning similar upgrades, and environmental activists say they will be looking to the Big Apple for inspiration.

“New York City probably has more streetlights than any other city in America,” said Eric Goldstein, New York City environment director for the Natural Resources Defense Council. “If it works in New York, it’s likely that other jurisdictions will pick up on the trend.”