Railways are generally thinner than roads with fewer intersections. They have smooth curves and bends with no abrupt changes in direction.
Generally there are a lack of access points, buildings and infrastructure along the railway line.
In Figure: 2.2.5.1a the colour of the railway line is similar to the surrounding area, due to the lack of pavement.
In Figure: 2.2.5.1b the spectral signature of the railway (red) is similar to the surrounding vegetation and landscape, as opposed to the road which stands out as bright blue.
Regional Considerations:
Figure: 2.2.5.1 Differentiation of Railways from Roads.