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Which road is considered the main road when there are no signs or signals?
There is no such thing as a “main road”. Since there are no signs or similar devices, you should adhere to the right-hand rule, which “[...] applies in the absence of road signs and road markings stating otherwise.” (Du och jag i trafiken, körkortsbok / teoribok [You and me in traffic], 28th Edition, page 139)
It is common to try to analyse situations like the one depicted, in order to arrive at what is logical and “should be the case”. This is not good. The right-hand rule does not take into consideration the size of the roads, their angles or how trafficked they are, etc. If there are no signs or signals = use the right-hand rule!
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