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2,298 miles of waterbound macadam roads cost $1,055.00 per mile.

2,387 miles of bituminous macadam, penetration method roads cost $510.00 per mile.

63 miles of bituminous macadam, mixing method roads, cost $181.00 per mile.

295 miles of concrete bituminous roads cost $1,050.00 per mile.

84 miles of first-class concrete roads cost $190.00 per

mile.

291 miles of block pavement roads cost $190.00 per mile. 5,611 miles of all types cost $750.00 per mile.

A review of the above summary would indicate that the various types could be grouped in three classes, namely: low, medium and high maintenance types, and when so grouped we have 438 miles of low maintenance type, including bituminous macadam, mixing method, first-class concrete and block pavement, upon which the average expenditure for maintenance was but $177.00 per mile per year; 2,387 miles of medium maintenance type, including bituminous macadam, penetration method, upon which the average expenditure was $510.00 per mile per year; 2,786 miles of high maintenance type, including gravel, waterbound macadam and concrete bituminous, upon which the average expenditure was $1,059.00 per mile per year.

If the low and medium maintenance types are grouped in one class, we have slightly over half the improved highways upon which the expenditure for maintenance is about $440.00 per mile per year, and slightly under one-half the total mileage upon which the expenditure for maintenance and repairs was $1,060.00 per mile per year.

In conclusion I desire to urge that in planning the improvement of any highway, the cost of maintenance be considered in connection with the other fixed charges which the municipal district, to which the cost of maintenance is proposed to be levied, has to sustain, in order to determine whether the maintenance of the improved highway may become a burden to the municipal district, whether same be town, county or State.

Factors for and Against Different Types of Pavement When Paving is Justifiable

By J. W. Cunningham, Member American Society of Civil Engineers

The paving question is a big one, and the subject of much fallacy and misconception. To tell the plain truth, a great deal that has been written and said on the subject is inspired by commercial interest, and from the scientific standpoint may be rated as pure "bunk." This paper will avoid technical details and attempt to touch only a few of the high points of paving.

The requirements for a surface on country highways differ to some extent from those of city streets; but country roads themselves also show a wide variation in conditions. From the standpoint of traffic, the scenic road, carrying only rubber-tired automobile traffic, may best be served by types of pavement quite different from those required for a road carrying steel-tired wagons, or for a road having a traffic of automobile trucks in their heaviest form. For those familiar with the situation in Multnomah County there may be cited as instances of varying requirements three roads: the Columbia River Highway, a purely pleasure drive; the Foster Road which serves a large farming community, and the Linn ton Road with a specialized traffic of very heavy oil trucks. Each of these roads imposes a different kind of wear upon its surface, and the requirements are fulfilled by different forms of pavement.

Climatic conditions also have distinct bearing upon the type of pavement. In western Oregon we have generally even temperatures, and heavy rainfall. Incident to the rainfall, the drainage and foundation conditions of our roads are often poor. In eastern Oregon, on the contrary, there is a greater range of temperature, less moisture, and usually stable foundations for roads. Directly related to the climate, the varying qualities of soil and foundation affect the pavement used, and must be given due study in making any choice.

There is no one pavement which is a cure-all for all conditions of traffic, climate and soil. Pavements are like patent

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medicines in that when one form is recommended as a shotgun prescription for every location we may conclude that it cannot be the very best in any place. The choice of a pavement is a problem for critical study. It is futile to attempt to judge a pavement by riding over it in an automobile, or to obtain accurate and truthful information from paving promoters and those advocating any particular type of pavement. Before we attain any notable degree of success and efficiency in the work of hard-surfacing, we must force the paving companies to compete on the basis of merit and price alone, and to keep out of politics.

PAVEMENTS SUITABLE FOR OREGON

To illustrate the different types of pavement which have been found suitable for Oregon conditions, attention should be called to a set of samples of pavement which were made by the Oregon Testing Laboratory, and are loaned for the Commonwealth Conference by the Portland Library Association. These samples represent sawed cross sections of what would be actually laid upon the road in accordance with the various standard specifications of the City of Portland. They are correct, and deserve careful study.

Of these pavements, there are three, the block pavements, brick, stone, and wood-block which are not generally adaptable for country roads, simply on account of their first cost. You will note that all are very thick pavements, with a heavy concrete base. They are economical under extremely heavy traffic. For example the Linnton road near Portland should have been, and without doubt ultimately will be paved with one of these three types. For the average highway their first cost is prohibitive.

The remainder of the pavements may be divided into two general classes, the asphaltic pavements and the cement pavements. In fact, if we overlook technical distinctions, we may say that all of the pavements generally adaptable for Oregon conditions are made up of different combinations of just three substances: Portland cement, asphalt and mineral matter in the form of crushed rock. The mineral matter forms

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