The article proposes a concept for analyzing ship routes, based on calculating the probability of polygon intersection. Methods for calculating spatial density, quantile routes, and interquantile areas were tested on AIS data on the year-round movement of Norilsk Nickel class vessels between the Barents and Kara Seas from 2009 to 2023. Based on an analysis of more than a thousand routes from Murmansk and Arkhangelsk to the port of Dudinka, we obtained estimates of seasonal variability in the position of routes: ship traffic mainly goes through the Kara Gates; in spring, when ice cover most interferes with navigation, some routes go north of the Novaya Zemlya archipelago. The proportion of the northern route reaches its maximum in May (38%). For most of the year, both the median route and interquartile area of the route positions (i.e., the area where 50% of all routes are located) are almost identical to the shortest path between the ports under discussion. In the spring months, median routes deviate significantly from straight lines and interquantile areas increase. This occurs because ship routes deviate from the shortest path and pass through outlying local areas with easier navigation conditions associated with polynyas, leads, and breaks in the sea ice cover.