On the Columbia Highway, 22 miles below Portland, they are building pavements of 3 inches of broken stone rolled into a medium clay loam for a width of 16 feet. On this rolled macadam base is placed 3 inches of asphaltic concrete, 45 pounds of asphalt being used to a thousand pounds of gravel. There is then placed an additional 2-inch wearing surface with 75 pounds of asphalt for one thousand pounds of gravel. The practice is to use 5 pounds of asphalt less per thousand pounds of aggregates on grades. It is said that the asphalt will move down hill, forming transverse ridges, where the grades are over 5%. The road was built in 1920 at a cost of $2.61 per square yard without subgrade. The traffic here is medium. Under the report of the Committee on Sub-base is given a further description of these Washington and Oregon pavements as related to their sub-base conditions. It is found that where the foundations are good and well drained either naturally or artificially that the pavements last well, but where they are built on new clay soils, especially where not well drained, all types of pavements fail. Where old macadam roads on clay soils have subsequently been surfaced with either asphaltic or concrete slabs the results are satisfactory. This points to a solution of our troubles with pavements placed on adobe. Such soils should first be prepared by rolling a layer of stone or gravel into the clay and preferably letting this be done by the traffic through one or more years' time.

Because of the great importance of this subject and the many factors that are still unknown, much further study should be given to it. It is not here presumed that all desired information is yet obtained.

There is co-operative work in road building between the Federal government and the State of Oregon. After much discussion of the relative merits of black base (asphaltic) and hydraulic cement pavements, the following alternate sections were adopted by the State and Federal authorities and alternate bids called for thereon. The asphaltic pavement is 16 feet wide with two-foot shoulders on each side 6 inches thick made of crushed rock. Rolled earthen shoulders extend for two feet outside of the rock shoulders. Four inches of graded macadam is rolled into the sub-base where on a new grade. On top of this rolled macadam there is placed a 3-inch asphaltic concrete base with a 2-inch wearing surface superimposed. The alternate hydraulic concrete section is a slab 16 feet wide, with shoulders as before, 61⁄2 inches thick on the sides and 7% inches in the center, reinforced with 1-inch bars around four sides of the slab and five 3-inch transverse tie bars between construction joints which are 30 feet apart. Bids were called on September 28, 1920, for about six miles of these two types of pavement on what is called the Oswego branch. The award was made for an hydraulic cement concrete pavement for $3.03 per square yard, to which must be added the cost of the steel.

The lesson to be learned from Oregon is that where broken stone has been rolled into the subgrade by traffic, as in the case of macadam roads, and a pavement placed thereon, it does not break down under service within short periods even when the subgrade is clay. Drainage, however, must be well cared for.

RELATIVE LIFE OF ROAD AND BOND

Table No. 19, page 79, shows the percentages of poor roads classified as to the years in which they have been built. Giving weights to mileage and carrying out the proportions shown for the various years, we have an average indicated life of state pavements for Southern California of 14.69 years. This age of road fairly corresponds to the estimated life of concrete slabs in Eastern States.

H. E. Bigler, Road Engineer for the Illinois State Highway Commission, assumes the life of a concrete road at fifteen years. About the same estimates have been made for the Maryland roads. These California pavements were built from the First and Second bond issues. Thirty

Showing crack between concrete shoulder and pavement, Orange County. It is difficult to get a bond between shoulder and pavement in this way. Water will get under slab through this joint.

This indicates the

Crack between repair made to concrete base with shoulder construction, Orange County. necessity of a wider original pavement or of a flexible oil macadam shoulder built at the time pavement is laid as called for in the plans.

per cent of our pavements are in poor condition practigally before the retirement of the bonds from which they are constructed has started. The logical outcome of such a policy of financing will lead either to the abandonment of the good roads program or the financial embarrassment of the State.

The State of New Jersey was the first to fully recognize by law the seriousness of a policy of building short-lived roads with long-lived bonds. Chapter 252 of their laws for 1916 is an act concerning the issuance of highways bonds. It states (Section 4, Sub-section L):

"Bonds used for the construction of roads and streets shall mature in not exceeding the following periods: If constructed of sand and gravel, 5 years; macadam or penetration process, 10 years; bituminous concrete, 15 years; block or sheet asphalt on concrete, 20 years; concrete constructed not less than 6 inches thick, 20 years. The most serious phase of the California Highway situation is this relation between the long-lived bond and the short-lived road. Our 4-inch pavements have demonstrated their inability to stand the traffic on our main trunk roads. It is quite probable that even with heavy slabs on the poor soils we will continue to have failures. Until it is demonstrated to the contrary, the assumption should be that the pavement, no matter how it is constructed, will be short lived. Probably the theory of the New Jersey law would be satisfactory. If the roads are long lived, they will be an asset which will be fully appreciated. The evidence at present, both in the East and West, however, is that the life of a concrete road under heavy traffic will not be over 15 years no matter how it is built. Even if it is assumed that the concrete slab after it has failed may be resurfaced with an asphaltic concrete, as is being practiced at present both in California and Maryland, the expense of this surfacing, if it is properly done, approaches the original cost of the concrete pavement and no adequate financial provision has been made for the carrying out of this policy. Even if such a top coating were put upon a broken down concrete slab, the life of the new pavement would be short as is indicated by conditions noted in the inspection of the road between Pomona and Ontario and at other places. The State of Washington is constructing the highways of that commonwealth by direct appropriation and at the elections, in the fall of 1920, declined to authorize extensive highway bond issues.

Pavements

GENERAL DEDUCTIONS FROM THE INSPECTIONS

From the field inspections and the studies, particularly of Table 20, page 101, and Table 19, page 79, the following deductions are made:

The greater portion of the roads that have been built by the State are of concrete on all classes of soils. The prevailing width of the primary pavements is 15 feet with a thickness of 4 inches without reinforcing. Shoulders of oil macadam, concrete or gravel are necessary on so narrow a pavement, yet of the 636 miles of state pavements constructed in the southern portion of the State 121.9 miles have such shoulders and 513.7 miles have not. The understanding has been general that they were to be built. As the larger cities and towns are approached, the policy has been followed of widening the pavements by the addition of these shoulders, or by the casting of additional slab of concrete 2 feet in width on each side of the original pavement.

On the basis of the definitions given on pages 81-84 the foregoing inspection report shows 30.5% of the concrete pavements that have been built in Southern California by the Highway Commission are classed as poor; 19.3% as fair; and 50.2% as good. Their average age is 4.24 years. (July 1, 1920.)

On October 5, 1920, the California Highway Commission adopted a thickness of slab of 5 inches for reinforced concrete pavements. The standard width of 15 feet is to be retained but increased in certain special instances. The numerous photographs accompanying this report indicate the general condition of both the good and the poor pavements.

With an average age of 4.24 years 30.5% of the pavements in the southern portion of the State are classified as poor, and by poor it is meant that within a short period of time they will either have to be rebuilt or resurfaced. The portion classed as fair has started to break down. Comparing the present condition of the pavements with their respective ages by years, a probable ultimate life of 15 years is obtained. Mr. J. N. Mackall, chief engineer of the Maryland State Roads Commission, estimates the probable length of life of eastern concrete roads under their very heavy traffic and frost conditions at 10 years, and under moderate traffic from 15 to 20 years. (Engineering News-Record, May 6, 1920.) This relates to the pavement only. The grade or road-bed, bridges and culverts representing perhaps one-third of the total cost may be considered as permanent works. It has been shown that the state highway bonds have a life from 45 to 50 years and that their retirement does not begin until from 6 to 7 years from the date of their issue.

Pavements that are built with funds raised with bond issues should, if possible, be so constructed as to last as long as the life of the bond, or not fail in a more rapid ratio than the bonds are retired. Otherwise a good roads program must ultimately be greatly involved.

As has previously been stated in the discussion of the traffic census, the number of heavy trucks on our pavements has increased enormously, as shown by Diagram No. 6, page 65. The prospects are that the traffic will continue to grow, both in number and weight of the trucks, unless the loads are limited by law and the enforcement thereof. It is unsatisfactory to continue building pavements whose probable life is fifteen years, under existing conditions, with our fifty-year highway bonds. There are many miles of roads that have been built in California that have been enjoyed not only by her citizens, but by many tourists who visit our State. They have been of value not only to the owners of trucks and automobiles, but to the community at large in that they have permitted of the cheap delivery of produce and the saving of time. They have resulted in a large advance in suburban and rural values. California highways have a fine national reputation. The experience which we are passing through with our road construction is similar to that of many other states. We are facing a new and enormous transportation problem that involves the public welfare. We must continue to have good roads. They should, however, be better built for longer life on a more rational basis of financing.