In level districts the adoption of straight or crooked, regular or irregular lines depends both on practical considerations and also on the artistic intentions of the designer. Transpositions are, however, only permissible in so far as they do not interfere with a clear view of the traffic. Convex changes of gradient are to be avoided in straight streets as far as possible. Concave levelling is to be preferred. Unavoidable stopping-points ought to be treated artistically as terminal points.
Every street ought as far as practicable to be planned individually.
A change of width in different parts of the same street may serve to add to its beauty. Self-contained street pictures are everywhere to be aimed at. For practical reasons it is desirable that the various lines of traffic should not intersect one another at one point. Spaces devoted to traffic lack, as a rule, one quality of artistic importance-viz. They can, nevertheless, be made to present a pleasing appearance.