The use of the concrete guard rail is one of the disadvantages of this road. The edges of the rail cannot be made rounding except by special forms and the rubbing of the tires against this rough surface would greatly reduce the tire mileage. In addition, the rail is so exposed to weather and hard wear that it cannot be relied upon to serve effectively for any great length of time. The placing of forms is also a considerable item of expense in building such a road. A method which would eliminate such an expense and at the same time provide a more practical rail would be an advantage. [Illustration: Figure 2. Cross section of concrete road. Scale--1 inch equals 2 feet.] It has already been said that guard rails are unnecessary with a thirty inch track except on sharp curves and otherwise dangerous places. However, where rails are necessary the wooden rail fastened by bolts embedded in the concrete as illustrated above, is quite effective and readily installed. This consists of a four by six inch plank placed on edge and drift-bolted to the concrete every three to five feet by a three-quarter inch bolt. These bolts are placed in the concrete when it is poured and should be embedded six inches. This will provide a rail less expensive to build than a concrete rail and one which will last longer and save on tires. Replacements are easily made by removing the nuts and placing a new plank in place of the old. With a guard rail of this type, there is left a twenty-six inch track for the wheels to run in. Experiments by W. D. Pence (Journ. West. Soc. Eng. Vol. VI, 1901, Page 549) on 1:2:4 concrete give an average value of 0.0000055 inches per degree Fahrenheit for the coefficient of expansion. The richer the concrete, the greater the change in dimension. Due to the expansion, in laying the concrete the track must be broken every twenty-five or thirty feet by placing a half-inch board in the ditch when the concrete is being filled in. Later this board is removed and the joint filled with asphalt so that the concrete may expand without danger of cracking the road. _Cost._ The best mix to use in building this road is what is known as the 1:2½:5. For one cubic yard of concrete, the following amounts of materials will be used for the above mix: 1.21 barrels of cement, 0.46 cubic yards of sand, and 0.92 cubic yards of stone. At the present prices, the cost for the materials for this road is about twenty cents a cubic foot or about $4,400 a mile. The total cost of the road including the necessary grading, ditching and labor, will be from $7,000 to $9,000 per mile.