Where traffic on the rural routes is heavy and, in the environs of cities, where it is desirable to discourage undue extension of road-bordering city growth, prohibition of access to the highway from abutting land, controlled access at specified points, and the closure or grade separation of all intersecting highways are essential.
If no prior right of access has existed, as will be the case where rural and suburban sections of the interregional routes are developed on new locations, it may not be considered essential to provide a local service road to abutting lands as an auxiliary of the interregional route. It will probably be necessary in such circumstances, however, to compensate the abutting owners for the denial of their right of access to the new facility.
Where a section of the interregional system is developed on the location of an existing highway to which all abutting properties have previously had unlimited access, it may be necessary to provide properties denied access to the through highway with other means of ingress and egress. This may be accomplished by the construction of roads connecting the affected properties with other existing roads, with improvement of such roads if necessary. In other cases, especially in suburban areas, it may be necessary to provide at each side of the through highway, parallel local service roads connected with the main artery at selected access points. The service roads may provide for one or two-direction travel, depending upon the amount of traffic to be served and the distance between points of access to the through highway.
It is in cities and their urban fringes, however, that the problems of provision for express traffic and denial of access are most difficult, complex and expensive of solution. As one of the interregional routes approaches a city, denial of access to it may be desirable for some distance outward from the point of first considerable roadside development in order to discourage the further excessive extension of settlement outward. Inward from the point described, at which the first of urban accesses should be provided, other access points should be chosen at not too frequent intervals, but so located as to serve with reasonable convenience the express highway needs of the more populous suburban foci.
Proceeding into the city proper, it is desirable that access to the highway be provided only at selected cross streets. As previously indicated, these should preferably be streets that cross the city or extend at least to the next adjacent express highways without interruption, in order that they may serve as clear and direct connections with the express route for as large a territory as practicable.
The usefulness of the express route for intraurban traffic is greatest for traffic between the outer residence areas and the city center. For this reason access points should be provided at shorter intervals near the city limits than near the center. Proceeding toward the center a point is reached at a substantial distance from the route terminus (say not less than a half mile nor more than a mile) between which and the terminus there will be no occasion for further access. Within this distance traffic to the city center can be accommodated more conveniently on the ordinary streets than on the express highway.
At least at the access streets, safe provision for intersecting traffic should be afforded. In the opinion of the Committee, this will invariably require the separation of intersecting grades. As necessary,
