Trunk roads are not classified based on their physical construction but rather their role in the highway network. In an urban scenario like DC, these are the most important highways that links commuters and trucks in and out of the city. See for example, Routes 1, 29, and 50 through DC, which serve as major arteries that link the city center to other major highways leading out of the city. Pennsylvania Avenue is also designated as a truck route in both DC and Maryland, and then becomes a freeway like Branch Ave does, linking the city to other major exurban communities.