Since short trips predominate in the traffic stream, many drivers are precluded from the use of a toll road merely because their trips are not long enough to permit them to take advantage of it.
Moreover, certain drivers who might use a toll road do not do so because of the toll, or for some other reason.
As an example, studies of traffic using the Maine Turnpike and the parallel U. S. 1 show that of the drivers whose origins and destinations were such that use of the full length of the turnpike was feasible, between 75 and 80 percent used the turnpike, the percentage increasing as the total traffic on the two routes increased. In contrast, less than 15 percent of those whose trips permitted the use of only part of the turnpike took advantage of it. Of the total vehicle-mileage on the two routes, excluding the mileage within the towns along U. S. 1, the percentage on the turnpike ranged from 38 to 50 percent, again with the percentage using the turnpike increasing as the total traffic on the two routes increased. Significantly, average traffic on U. S. 1 in 1954 had regained its level of 1947, the year before the opening of the turnpike.
Thus, even though a toll road may be readily self-liquidating, it can never relieve some public agency from the responsibility of continuing to provide local service and service for through travelers who, for whatever reason, prefer not to use a toll road.
On the other hand, a properly located and designed free road can serve both the through and local traffic. As an indication of the limitation of traffic service that can be provided by toll roads, it was estimated that the Interstate System, if its inadequate sections were completed as toll roads located in keeping with current practice, would serve only two-thirds of the traffic that the system would serve if it were completed as a free system.
In the more congested areas, where traffic volumes are sufficient to require two or more roughly parallel routes, there is advantage in locating one to accommodate principally the through traffic, whether it be toll or free, and another to accommodate local or shorter-range movement.
In the more usual case, however, a single facility appropriately located and adequately designed can accommodate the traffic for many years to come. To build a toll road in such a situation might be financially feasible. And the toll road would relieve to some extent congestion that might exist on the free road that must also be maintained. Further, by this measure of traffic relief, it might be found considerably less costly for the responsible public agency to maintain the free route in condition suitable for its remaining traffic than it would be to provide and maintain a single facility for the entire traffic flow through the area. Despite whatever saving may accrue to the public agency, however, the fact remains that the two facilities must be maintained, one from public funds and one from funds from private sources ; and regardless of the source of funds the total cost will in all probability be greater, and the greater cost is, of course, borne in one way or another by the public.
Effect on programing of improvements
The impact of a toll road is, of course, not confined to any particular system of roads, but because most existing and prospective toll roads lie along the general lines of the Interstate System, the effect is greatest on the planning and construction of that system and on the other Federal-aid roads closely integrated with the Interstate System.
