Page:Toll Roads and Free Roads.pdf/104

76 It is concluded that:

''The system of roads selected, conforming closely to the direction of section 18 of the act of June 8, 1938, vs feasible of construction at approximately the cost indicated. Moreover, it is probable that no reasonable change in the precise location of a system of approximately the same extent would materially affect the indicated average cost per mile.''

ESTIMATES OF ANNUAL COST AND REVENUE

It is assumed that construction on the selected routes, if it is undertaken, will be completed one-half by January 1, 1944, and the remaining half by January 1, 1946. Without any significant error it can be assumed that the whole system would come into use on January 1, 1945, with collection of revenues from that date on the entire system.

Traffic estimates have been projected to 1960, and cannot, with reasonable assurance of accuracy, be projected beyond that year. From January 1, 1945, to December 31, 1960, is a period of 16 years, and it is for that period only that revenues can be estimated with substantial accuracy.

The roads, as built, would have a probable average service life, as a whole, extending far beyond this 16-year period. Some elements of the construction obviously have longer lives than others, but all elements, with the possible exception of some very minor ones, such as signs, fencing, etc., should last well beyond the 16-year period.

For example, the probable average service life of the surfaces or pavements may be assumed to be at least 30 years. This life period reflects experience tables of similar past construction, together with the more favorable quality of the proposed construction. The estimated construction cost of the pavements, including curbs and accesses is $682,231,200, which is 23.5 percent of the $2,899,770,000, estimated as the total cost of all construction and right-of-way. The average life of the graded roadbed and right-of-way may be assumed to be at least 100 years. Only a general change in the geometric design of the roads as built could materially affect the accuracy of this assumption. The estimated cost of right-of-way, clearing and grubbing, grading, minor drainage, topsoil, seeding, and planting, totalling $1,014,044,700, represents 35 percent of the estimated total cost. The average life of major structures, such as bridges and tunnels, similarly may be estimated conservatively at 60 years, although for the modern types of structure proposed such a life period is probably short. Bridges and tunnels are estimated to cost $1,121,797,800, which is about 38.5 percent of the estimated total cost. Other miscellaneous items of the construction, such as guardrails, signs and markers, and fences are generally of shorter life than the three major items above mentioned Their estimated cost, $81,606,400, is only 3 percent of the total estimated cost. If these elements are assumed to have an average service life of only 10 years, the probable composite average life of all elements of the routes as constructed, including their rights-of-way, would be: $\frac{23.5 \times 30 + 35.0 \times 100 + 38.5 \times 60 + 3.0 \times 10}{100}=65.5 \text{ years}$