Ring 1, 2 and 3 are highway rings in and around Oslo. Ring 4 and upwards is the unofficial names of the gravel heavens that surround Oslo, and are really easy to get to from the city center. Can be run either way. The gravel is very good, and can normally, especially when it's dry be ridden on 25 mm slick tyres.
THE ROAD IS CLEARED FROM SNOW THROUGHOUT WINTER. If there has been very recent significant snowfall, the snow clearers might not have gotten around to it before a day or two has passed.
The roads here are used for logging, so you might encounter cars, even though the road is closed for cars without a permit. Make sure to keep right to avoid injury.
Please be aware that the road is used by a number of pedestrians as well, and they can pop out from a path very suddenly, so be mindful with regards to speed and position on the road. Be especially aware down Sørkedalen on the west side, which is especially beaming with pedestrians, kids and dogs on the weekend.
Dødarebakken, northeast of Kikutstua has a very sharp curve. Take care if going in the western direction, as the hill is steep, and you might not make the turn on gravel. There is a path going in the middle of the curve, if all else fails, aim for it for a better shot at surviving :)
Kikutstua is a logical place to stop for coffee, open most days, and even have a vending machine and a room to sit in if the cafe's closed. Kikutstua even have accomodation, but probably needs to be booked in advance.
Other cabins that may or may not have service is Kobberhaughytta and Finnerud on the western side.
Enjoy the ride, and make sure to tip your cap to fellow cyclists and other travellers.