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64 previous commitment to the traditional rectangular street plan. It is highly desirable, therefore, that the location and plan of the new highways in these areas shall be developed in harmonious relation with other appropriate uses of the now vacant land. Wherever possible, plans for all uses of the land should be jointly developed and acquisition for all purposes of public use should proceed simultaneously.

In any case, if the new city-entering highways are located through existing wedges of undeveloped lands, they must be connected with well developed existing suburban areas, which are usually located along the present main highways, in order to serve effectively the arterial needs of these communities. Adequate cross highways at suitable points will provide these connections. And continued around the city, from one new arterial and one existing main highway to another, these connectors become the circumferential routes which are discussed later in this section. Some of these circumferentials, especially those forming the outer belt, may appropriately belong in the interregional system, as they would serve both to distribute the city-bound interregional traffic around the city to the point nearest its destination, and also to transfer through traffic around the city from one route to another.

It will be at once apparent, however, that if the improvement of main highways in the past has resulted in the stringing out of city growth along them, the superior improvement contemplated for the new arterial routes would have the same effect in exaggerated degree. The improvement of the interregional system should be so designed as to discourage ribbon development and the unwise subdivision of large tracts of suburban land. Special preventive measures will prove helpful in this connection. One of these measures, applicable at the appropriate stages of city growth, would be to provide additional circumferential routes (as discussed in the following section), and then, as the interradial spaces widen, to add branches to the radial arteries, thus encouraging uniform development of whole areas rather than ribbon-like settlement along the radials. Another, which involves no principle of route location, is mentioned here only because of its bearing upon city development. It is the control and limitation of access to the arterial routes.

Unlimited access to the existing main highways has undoubtedly encouraged the outward extension of settlement along them. Per contra, the denial of access to the new arterial highways for a substantial outward distance beyond any desired points on these highways would probably discourage the creeping of settlement along them much beyond the selected points, and this is endorsed by the committee in principle.

Circumferential and distribution routes.—Although, as previously indicated a large part of the traffic on interregional routes approaching the larger cities will generally have its origins and destinations in the center of the city, substantial fractions will consist of traffic bound to and from other quarters of the city. Another portion—its volume depending usually upon the size of the city in relation to the sizes of other nearby cities—will consist of traffic bound past the city.

To serve this traffic bound to or from points other than the center of the city, there is need of routes which avoid the business center. Such routes should generally follow circumferential courses around