14 BULLETIN" 136, U. S. DEPARTMENT OF AGRICULTURE. 



Instances are also known where concrete road surfaces have shown a 

 very high percentage of annual wear. In other cases there is appar- 

 ently no measurable wear. If the road surface is built with the 

 proper mix of concrete and carefully placed, it apparently should 

 last indefinitely and not rut. Some cleaning of the surface and 

 patching of joints and small depressions will be necessary at all 

 times, so that the maintenance can not be entirely neglected. 



The cost of repair and maintenance upon brick highways is very 

 low. In most instances, where the construction is as nearly perfect 

 as possible, almost no maintenance charges have resulted. Perfect 

 construction, however, is seldom obtained. 1 It is not unusual to 

 find depressions and points of wear in brick roads, but it is less com- 

 mon than formerly. Brick roads are now usually constructed on a 

 concrete foundation, with very carefully selected vitrified brick, and 

 with the joints filled with cement mortar. Their annual maintenance 

 costs, although low, are not on record with sufficient continuity to 

 supply accurate data. 



It has not been customary for officials to face frankly the cost 

 of maintenance and repair on bond-built highways at the time the 

 bonds are issued and before construction begins. In fact, in the 

 majority of cases where bonds have been issued by local authorities 

 there has been no provision whatever for maintaining the roads when 

 built. This is perhaps the gravest defect in the project of building 

 highways by issuing bonds. The cost of all maintenance and repair 

 over a series of years has ranged in the past from 6 to 10 per cent of 

 the original cost of construction on the average and varies with the 

 type of construction. Concrete roads and brick roads apparently 

 are a marked exception to this rule. In future construction where 

 the type of road is properly adapted to traffic and with careful main- 

 tenance from the outset the percentage of repair and maintenance 

 cost should be lower. 



THE BOND ISSUE. 



Sinking-fund bonds. — The majority of highway bonds now 

 outstanding have been issued as straight terminable bonds to be 

 retired by sinking funds. Many such bonds now run for excessive 

 terms. Although the term varies from 10 to 40 years, the average 

 is nearly 25 years. 2 The fund to retire the bonds is accumulated by 

 annual installments paid by the taxpayers and is supposed to draw 

 interest continuously and to accumulate a sufficient amount to dis- 

 charge the debt at maturity. The interest which the sinking fund 

 draws is usually from 1 to 2 per cent less than the interest paid for the 

 loan. Five per cent highway bonds are common with the sinking 

 fund calculated to draw 3^ per cent interest. Table 6 shows the 

 annual payments to the sinking fund necessary to accumulate $1,000 



i Cf. Bulletin 23 of the U. S. Department of Agriculture. 



2 Some issues— notably New York State— run 50 years. Cf. Appendices A and B. 



