Tar macadam roads are constructed the same as other macadam roads, except that the top layers of broken stone are covered with hot tar before they are rolled into place.
Costs Compared.
If $70 per mile be taken as the cost of constructing an earth road two rods wide, the cost of building one mile of gravel road will build some fifty miles of earth road; one mile of ordinary macadam will build 300 miles of earth road; one mile of tar macadam will build 360 miles of earth road; and one mile of asphalt pavement will construct 600 miles of earth road.
The Earth Road a Portion
of Better Roads.
An important argument in favor of the earth road is the fact that when it is laid out and constructed, it is the beginning of a first-class gravel road, a first-class macadam road, or a first-class tar macadam road, so that by getting the earth road made, the individual interested primarily in the construction of hard roads has succeeded in getting the hard road well begun.
Roads in Sand and Soft Clay.
While nearly everywhere in Utah the soil is such that it will make a good earth road, there are parts in which the soft clay is filled with alkali, and there are other parts where there are extensive stretches of sand. Neither of these alone can be made into an earth road that will be a good, passable road all the year round. The sand road is best in wet weather, while the alkali road is best in dry weather. If, however, the soft clay and the sand are so mixed on the road that the clay just fills the openings or interstices between the grains of sand, and yet this quantity is not so large as to keep the grains of sand from touching or coming in contact with one another, the road, if properly and constantly maintained, will be a good one.
Cost of Maintenance.
Since proper maintenance is an important part of the work on ordinary roads, its cost will be considered briefly.
The repairs and maintenance on an asphalt pavement cost from 9 to 60 cents per square yard annually, or for a two rod road the cost is from $1,750 to $11,600 per mile per year; on a tar macadam road the cost is from $2,000 to $4,000 per mile per year; on a gravel road it is about $40 per mile per annum, while for $5 per mile per year an earth road can be kept in a condition of repair that will surprise those who have not used the split-log drag on such a road.