The 1.1 million kilometres of roads shown on the map form a national road network that connects people and goods from one community to another in Canada and to the rest of the continent. On the map, roads are classified based on the population of the communities the roads connect; combined, the communities on the map represent 78% of the total population in 2001. Principal road corridors connect major cities with a population greater than 49 999 and major ports of entry into and out of the country. Secondary road corridors connect medium-sized populated places (of between 10 000 and 49 999) to the principal road corridor. Major roads connect the smaller-sized populated places (of between 1000 and 9999) to the principal and secondary road corridors. Minor roads connect populated places with a population less than 1000 to the principal and secondary road corridors, and to major roads. Minor roads also include roads connecting Indian Reserves. Local roads include all other roads not directly connected to the network by the population between two populated places. Winter roads serve remote and northern communities in the winter or when weather conditions permit travel.