Lights turned back on at five Buckinghamshire sites
Streetlights have been turned back on at five of the 46 Buckinghamshire locations that were part of a three-year switch-off trial.
At four of the sites the number of accidents increased, although on average injury collisions fell by 26%.
The trial, implemented by Transport for Buckinghamshire, finished at the end of 2011.
The county council chose areas that should have lights turned back on after studying data and public feedback.
Councillor Peter Hardy said: "We had this lengthy trial to ensure that we made the right decision on a site-by-site basis.
"My engineers have advised me on their proposals where they feel any enhancement measures are required and I am satisfied with their recommendations."
The streetlight switch-off was introduced in two phases between August 2007 and September 2008 and a public consultation on the proposals came to an end on 15 April this year.
The council said it saved more than £260,000 in energy costs and 1,625 tonnes of carbon dioxide.
Three of the four sites where collisions increased were roundabouts at Nash Lee and South Street in Wendover and the Radclive roundabout on the A421.
A length of the A413 from the Kingsway roundabout to the railway viaduct at Chalfont St Peter was also identified as having a higher accident rate.
The number of collisions decreased at Studley Green on the A40 near Beacons Bottom, but other trial data showed that lighting was still needed there.
A site at the A40 in Denham was suspended from the trial in February 2011 after a pedestrian crossing, which required streetlighting, was installed to replace a damaged footbridge.
At the other 40 sites, lights will remain switched off but further improvements to signage, bollards and road markings will be made at several, before the lighting columns are removed.