on this important route at the city limits could be diverted over a bypass route around the city, the volume of traffic on the connecting streets at the center of the city would not be reduced in any large proportion; and, as previously stated, no large part of the existing traffic at the city entrances could be diverted.
At all large cities, however, and many smaller ones, there is need for the construction of what are called in this report belt-line distribution roads. Such roads have some of the characteristics of bypass routes, and may actually serve to bypass a considerable amount of through highway traffic around the city. Their primary purpose, however, is something different.
From most large cities a number of relatively important highways radiate in several directions. Between each of these highways there is a certain interchange of traffic that normally enters the city only because it is there that the routes have their junction. A major part of the traffic on each of the routes has its origins or destinations within, but in various parts of, the city, some near and some remote from the points at which the respective routes enter the city.
That portion of the traffic from each of the roads that is bound to or from the center of the city is best served, if it is a considerable movement, by the transcity connecting routes and expressways previously described. These same kinds of facilities also most directly serve the needs of traffic between each city-entering highway and points in or beyond the city that lie approximately diametrically opposite its point of entrance.
But, for those parts of the traffic on each entering highway that are (a) interchanged with other entering highways not nearly opposite across the city and (b) originated in or destined to sections of the city similarly situated, the facility that will generally provide the best service is a circumferential or belt-line route forming an approximate circle around the city at its outer fringe.
The principal function of such a route is the distribution of traffic approaching the city on any highway, either to the other highways to
