Part-Night Lighting: How Dimming and Curfews Cut Light at Night

What Is Part-Night Lighting?

Part-night lighting runs outdoor fixtures on a schedule instead of dusk to dawn. Lights come on at dusk, then dim or turn off at a set hour, such as midnight. Some systems restore full output before dawn for early commuters, deliveries, or staff. The strategy can apply to every fixture on a site or only to the fixtures that are not needed overnight.

Two versions are common:

• Part-night switch-off: selected lights turn off completely during set hours.
• Part-night dimming: lights stay on at reduced output during set hours, then return to full output when needed.

Where Part-Night Lighting Is Already Working

Streetlights in Wales: part-night since 2008

Pembrokeshire County Council manages "around 15,800 street lights and 1,400 illuminated signs" and has operated part-night lighting since 2008, with an "approximate midnight-to-5.30am GMT" switch-off. Exceptions cover significant night-time collision sites, crime concerns, and busy town-centre areas. A proposed 2026 policy adds guidance on dimming, energy efficiency, and protecting dark skies, according to The Pembrokeshire Herald (November 1, 2026).

Seasonal blackouts for seabirds in the Azores

On Corvo in the Azores, public lighting is "completely turned off at 9:00pm, until 4:00am, for five nights" at the end of October to protect Cory's Shearwater fledglings. A Portuguese Society for the Study of Birds (SPEA) survey of 207 residents found unanimous support, according to Good News Network (November 1, 2026).

Park and court curfews in the United States

In Manteno, Illinois, the village board approved lighting for six pickleball courts and set a 10 p.m. closing for nearby residents, "which means lights off," according to Shaw Local (November 3, 2026). A recreational lighting curfew is part-night lighting applied to a single site.

Why Owners Choose Part-Night Lighting

1. Lower energy and maintenance costs. Lights that run fewer hours use less electricity and wear more slowly.
2. Less light pollution. Dimming and switch-off reduce skyglow and light trespass during the hours when wildlife and neighbors are most affected.
3. Ordinance readiness. Many local ordinances limit when parking lot and recreational lights may operate, such as no operation after midnight or after a set curfew. Maine's LD 1934, for example, requires nonessential public outdoor lighting to be off overnight, and Kerrville, Texas calls for security lights on motion sensors or curfews.

Safety First: Where to Keep Lights On

Part-night lighting is a site-by-site decision, not a blanket rule. Pembrokeshire's policy keeps lights on at significant night-time collision sites, crime-concern areas, and busy town centres, and removes lights only "where a risk assessment finds that safe." Private sites should follow the same discipline. Keep full light at entrances, walkways, stairs, loading areas, and any location with overnight staff or security cameras. A lighting specialist can identify which fixtures can dim or switch off and which must stay at full output.

Controls That Make Part-Night Lighting Work

• Time clocks: turn lights off at a set hour. Electronic time clocks adjust for sunrise and sunset times.
• Photocells combined with time clocks: the photocell turns lights on at dusk; the time clock turns them off at the scheduled hour.
• Bi-level occupancy sensors: dim lights to a set percentage of full output when an area is empty and return to full output when someone arrives. They require LED fixtures with dimmable drivers.
• 0-10V dimming, DALI, and wireless controls: schedule dimming across many fixtures. DALI is managed by the International Electrotechnical Commission through the IEC 62386 family of standards.

Learn more about each option on our parking lot lighting controls page.

Fixtures Built for Part-Night Lighting

Part-night lighting works best with dark sky friendly fixtures that are already full cutoff and shielded. For coastal and wildlife-sensitive sites, 590nm amber sources pair well with seasonal part-night schedules.

How to Plan a Part-Night Lighting Program

Part-Night Lighting Frequently Asked Questions

What is part-night lighting?

Part-night lighting is a control strategy that dims or switches off outdoor lights during late-night hours when few people are present, then restores full light before morning activity.

What is the difference between part-night lighting and dimming?

Part-night switch-off turns selected lights off completely during set hours. Part-night dimming keeps lights on at reduced output during those hours. Many programs use both.

Is part-night lighting safe?

It is safe when it is planned site by site. Pembrokeshire County Council in Wales keeps lights on at significant night-time collision sites, crime-concern areas, and busy town centres, and removes lights only where a risk assessment finds it safe.

What hours does part-night lighting usually cover?

Schedules vary by owner and ordinance. Pembrokeshire County Council switches off many streetlights from about midnight to 5:30 a.m. Corvo in the Azores turns off public lighting from 9 p.m. to 4 a.m. for five nights each October to protect seabird fledglings.

What controls do I need for part-night lighting?

A time clock, a photocell combined with a time clock, a bi-level occupancy sensor, or a networked system using 0-10V dimming, DALI, or wireless controls. Dimming requires LED fixtures with dimmable drivers.

Does part-night lighting help protect wildlife?

Yes. Reducing light during late-night hours limits disruption to nocturnal wildlife. On Corvo in the Azores, seasonal blackouts protect Cory's Shearwater fledglings each October.

How do I know which lights can be dimmed or turned off?

Request a photometric study. It shows light levels across your site at full and dimmed output, so you can keep light at entrances and walkways and reduce it where it is not needed.