Let's make an important distinction between roadways and highways. Roadways are common resources (rivalrous and non-excludable). Limited access highways are club goods (rivalrous and excludable).
Any network structure (data, telephone, water, electricity, sewerage, roads, highways) has increasing returns to scale, and tends to result in natural monopolies. We recognize that they aren't normal market goods, and regulate them accordingly. Sometimes we mandate competition (internet services), sometimes we socialize them (municipal water and sewer), and sometimes we create regulated monopolies (power and natural gas).