Road grid does little when there's several cm of snow on top of the ice. It's a very slippery combination.
During winter the sidewalks rarely get the snow removed. So unless there's dedicated bike lanes, which there are still rather few of, you'd have to bike in the middle of the road. Which, due to the topography, would mostly mean holding up the traffic big time.
They're building more here tho, so unless we get a shift in power next year (local elections), the situation should be much better in a few years time.
They've also said they'll focus keeping the bike roads clear during winter, currently a big issue for myself.
During winter the sidewalks rarely get the snow removed. So unless there's dedicated bike lanes, which there are still rather few of, you'd have to bike in the middle of the road. Which, due to the topography, would mostly mean holding up the traffic big time.
Here are some news articles from last winter which contains some illustrative pictures: https://www.aftenposten.no/norge/i/m60VB0/Mer-sno-i-vente-pa... https://www.aftenposten.no/osloby/i/ka3kLj/Oslo-vinteren-har...
Of course it's not always that bad, but it's usually not a whole lot better either for most of the winter.