Another method of making economical comparisons is shown in the table and plot following: ---------------------+------+------+----------+--------+ | 1 | 2 | 3 | 4 | | | |Bituminous| | Item | | | Macadam |Portland| |Earth |Gravel| and | Cement | | Road | Road | concrete |Concrete| ---------------------+------+------+----------+--------+ First cost per mile |$1,000|$5,000| $10,000 |$20,000 | Annual Interest, 5 | | | | | per cent | 50| 250| 500 | 1,000 | Annual Maintenance | 250| 250| 500 | 100 | Life of surface, yrs.| 0| 5| 10 | 20 | Cost of resurfacing | $ 0|$2,500| $ 5,000 |$15,000 | Annual Sinking Fund | | | | | 3¹⁄₂ per cent | 0| 466| 427 | 530 | Annual Total Cost | 300| 966| 1,427 | 1,630 | Daily Cost, per mile | 0.82 | 2.74 | 3.90 | 4.45 | ---------------------+------+------+----------+--------+ ---------------------+----------+-------+------- | 5 | 6 | 7 | | | Item | Sheet | Brick | | Asphalt | Stone | Wood |Bitulithic| Block | Block ---------------------+----------+-------+------- First cost per mile | $30,000 |$40,000|$50,000 Annual Interest, 5 | | | per cent | 1,500 | 2,000| 2,500 Annual Maintenance | 100 | 50| 50 Life of surface, yrs.| 20 | 25| 25 Cost of resurfacing | $15,000 |$25,000|$35,000 Annual Sinking Fund | | | 3¹⁄₂ per cent | 530 | 884| 899 Annual Total Cost | 2,130 | 2,934| 3,449 Daily Cost, per mile | 5.84 | 8.03 | 9.46 ---------------------+----------+-------+------- [Illustration: _Plot showing cost of several types of roads under varying traffic density. When the traffic density of road No. 1 (Earth and sand clay) becomes greater than 300 or 400 vehicles per day the curve would turn up because the maintenance costs would be increased. Similarly for Nos. 2 and 3 for 1600 to 2000 vehicles per day._] SELECTED REFERENCES “American Civil Engineers’ Pocket-Book,” Sec. 15, Art. 4, John Wiley & Sons, New York. “American Highway Engineers’ Handbook,” p. 1360, John Wiley & Sons, New York. American Society of Civil Engineers, _Proceedings_, 1918, p. 2327. ANDERSON, ANDREW P., “Modern Road Building and Maintenance.” Hercules Powder Co., Chicago. _Automotive Industries_, “The Motor Bus Field as a Market for Trucks,” Vol. XLV, pp. 627-628, Sept. 29, 1921; “Weight of Trucks,” May 18, 1922. BLANCHARD AND DROWNE, “Textbook of Highway Engineering,” Chap. II, John Wiley & Sons, New York.