street.The business-generating potentiality of a heavy traffic stream is so great that there is an immediate development of a great variety of roadside establishments all along every new heavily traveled route that is created. Every new highway also, especially in the vicinity of cities, immediately encourages residential development and attracts commercial establishments more interested in the new facility provided by it than in catering to its traffic.
If, therefore, a bypass or belt-line route is to remain the through-traffic facility it is intended to be, it must be protected from the encroachment of bordering developments that would quickly engulf it and destroy its special character. This means that bypass routes must be built as limited-access highways, cut off from the bordering land except at a very limited number of points, and separated from all but a very limited number of the cross streets and highways intersected by them.
As right-of-way difficulties have been shown to have been paramount in the past in discouraging the enlargement of main highway facilities at the entrances to cities and halting the provision of really adequate connections across cities and expressways into cities, so also they have thus far discouraged in many cases the construction of any kind of city belt-line or bypass facilities, and have absolutely prevented the protection of such routes from the encroachments referred to above. In this latter connection there enters also something more than the usual difficulty of obtaining space for the highway from unwilling or rapacious individuals. There enters here the further difficulty, rarely dealt with heretofore, of publicly acquiring the legal authority or right to prohibit entrance upon the highway except at designated points. Railroad companies have acquired such rights with respect to their rights-of-way, and there have been a few instances in which they have been similarly acquired for highway purposes.
Although it has not previously been mentioned the same need for the control and limitation of access will exist frequently in the development of main highways, particularly at city approaches and in the provision of adequate transcity connections and express highways, and wherever this need exists it obviously will complicate and render more expensive the acquisition of required rights-of-way.
In the construction of future belt lines and bypasses control of lateral access and separation from the grade of cross highways at intersections always should be provided. Only by so doing can the bypasses be preserved for their proper function of serving through traffic. So protected, the cities can expand beyond the circuit routes provided without interfering with the discharge of the duty of such routes. Without such protection, particularly at the larger cities, we must face the necessity of building at frequent intervals a succession of intended belt-line or bypass routes each further removed from the cities, and never for long accomplishing the intended purpose.
BALTIMORE AS AN EXAMPLE
The location and design of transcity connecting streets, express highways, and belt lines or bypasses is a matter that requires particular study of the physical and traffic conditions peculiar to each city. For purposes of illustration only a limited study has been made of the conditions existing at Baltimore, Md., and a general plan involving a combination of the various types of city-vicinal facilities as
