For one of the author's standard-type highway-bridges, having four per cent grades on the approaches and sand foundations at a depth of 125 feet below high water, the other conditions being as previously indicated for the crossing with one high and one low bank, the estimated costs of structure were as follows:

For the layout with two low banks. the costs of the two structures were as follows:

The main reason for high-level structures costing more than low-level ones is the greater lengths and costs of the approaches; and as in highway bridges the grades thereon are much steeper than on railway bridges, their ratios of costs of high-level and low-level structures are less.

It will be necessary to compute carefully for each type the total annual costs of maintenance, repairs, sinking fund, and operation, capitalize these totals, and add the results to the estimates of first cost. A comparison of these sums will determine the financial economics of the two types compared.

To be strictly accurate, however, in determining these comparing figures, one should estimate the total annual costs of all kinds of power expended in climbing the approaches, capitalize these, and add them to the previous sums before making the comparison; but, as considerable guess-work would be involved in making such a computation, it might be exact enough for all practical purposes to assume that the total annual costs of power are the same for the two types of structure.