HIGHWAY BONDS. ig 
In issuing bonds for building highways the element of investment 
is of great importance. The allowable variations in grade and align- 
ment are considerable, as are also the variations in the types of drain- 
age structures. But there exists always a minimum standard below 
which it is uneconomical for any community to build on borrowed 
money. 
It is manifestly poor policy to build an expensive surface or 
a relatively long-lived surface on defective grades with poor align- 
ment, or where the drainage features are short-lived and temporary. 
Construction should be so adjusted to the service needed that its 
purpose is accomplished without waste. A county with impassable 
muddy clay roads must obtain, with a bond issue of $100,000, a 
maximum mileage of improvement. If roads are constructed cost- 
ing $10,000 per mile, but 10 miles can be built. It is quite proba- 
ble that the best economic result will be obtained by building 40 
- miles of road at a cost of $2,500 per mile. This money should be 
spent largely for enduring features, such as grading, drainage, etc. 
The common error, however, in county bond issues is to fix the 
sum to be voted upon and then to demand an exorbitant mileage 
for that sum. There is presented in Table 5 and in Appendix C the 
percentage of the cost of drainage and grading, exclusive of surfacing, 
and the percentage of cost of the surfacing on a considerable mileage 
of road from several States. 
Not all the surfacing need be a perishable feature. Itis becoming 
more and more common to construct roads with surfaces built in 
two courses, the lower of which is regarded as a permanent feature 
of construction. This is particularly true of those types of road that 
are built with concrete foundations for bituminous-macadam, brick, or 
asphalt surfaces. Most hard roads are now seldom allowed to wear 
into the foundation course of the surfacing. It is probably conserva- 
tive to regard 40 per cent of the surfacing cost of macadam or more 
enduring pavements as a cost for permanent features. Well-built 
macadam roads, from the recorded costs in Table 5, would therefore 
indicate a cost of 62 per cent of the total cost for permanent features 
and bituminous-macadam roads about 56 per cent. This method of 
estimating can not be applied to gravel or any natural soil road. 
Under most existing systems of maintenance the entire surfacing of 
such roads steadily deteriorates. It is generally accepted that roads 
built with surfaces entirely of concrete or with a brick pavement and 
a concrete foundation are permanent. It is not, however, yet known 
how long the best concrete surface will wear and it is certain that 
serious failures of concrete surfaces have resulted from poor construc- 
tion. The best vitrified brick surfaces may have a life of 30 years 
or more, but repairs will usually be required and sufficiently exten- 
