Terje Moe Gustavsen, who is director of the agency, said NPRA strongly advises against sex on roundabouts, as well as running naked on bridges.
Traditional celebrations (russefeiring in Norwegian) by Norwegian upper secondary school (gymnasium) pupils in their final spring semester usually start on around April 20th and end on May 17th, Norway's national day.
Students commonly wear coloured overalls and hire buses, cars or vans in which they travel around local towns. The young school leavers often celebrate continually during the month-long period, and drunkenness and public disturbances are regularly linked to the celebration.
Traditional challenges, which vary regionally, are known as russeknuter, literally ‘graduate knots', due to knots being tied in students' graduation caps as a mark for each completed challenge.
“Graduation challenges are fine. A lot of fantasy is spent on thinking up funny and sometimes challenging tests. Seen from an ‘adult' perspective, some of the rules might seem silly or weird, but it's meant as a way to express fun and celebration,” Gustavsen wrote in a blog published on NPRA's website.
Nevertheless, the NPRA director advised against roundabout sex.
“Everyone knows that it is a traffic hazard [for pedestrians] to be in and around roundabouts,” he wrote.
Gustavsen issued the advice on behalf of the agency after reading about challenges in the town of Ringsaker.
One of the challenges in that town involves a prize being awarded for having protected sex on three different roundabouts, Gustavsen wrote, citing a report in newspaper Ringsaker Blad which listed 100 such challenges for local students.
Gustavsen's message also made mention of a challenge involving a naked run over the 1.4 kilometre long Mjøsbrua bridge that crosses Lake Mjøsa near the town.
“It is probably not dangerous for a runner to be without clothes on the bridge, but people driving could get such a surprise if they see naked people on the bridge, they might forget they are driving,” he wrote.
“I hardly want to be seen as a killjoy or as Aunt Sofie. But dear graduates: Ringsaker has 97 other challenges to choose from. I'm sure that is also the case elsewhere in the country,” the NPRA director added.