Road capacity is a function of linearity as linear roads usually have more capacity than curved roads. This is also linked with the road surface as historically curved roads tended to have a soft surface while linear roads tended to be paved. On a soft surface road conditions deteriorate with traffic, which requires constant maintenance. Weather events such as rain can also significantly deteriorate soft road conditions. People are minimalists, so trails always followed the easiest or shortest path, which is still the case today. Well-trodden paths tend to be preferred since they imply less effort (energy consumption). On plains, the straight line was the shortest path chosen, while the contour line was privileged in mountainous areas since it minimized efforts. The need for linear roads incites the construction of hard (paved) surfaces which involve a substantial modification of the landscape with bridges, tunnels and the leveling of surfaces.