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Fig. 214

A Swiss village street; macadam with stone curb and gutter.

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CHAPTER VII

GENERAL OBSERVATIONS

All the cities to which these notes refer were inspected at least once, the time devoted to them varying with their importance from an aggregate of nearly four weeks in London to only a day or less in some of the minor towns. The statistics given ve been obtained in all cases from the authorities charged wit the work of pavement maintenance, either by direct interview or subsequent correspondence. A few general deductions can be made as to the prevailing European practice for city pavements.

ORGANIZATIONS FOR HIGHWAY CONTROL

In the introduction there has been given a brief statement as to the two forms of organization usually found in control of highway construction in the European cities. In English municipalities this work is under the direction of a city engineer or borough surveyor reporting to an elective municipal council and controlling street pavement maintenance and construction, both footway and carriageway, including sweeping and cleaning, sewers, lighting and other forms of municipal activity.

In the Scotch cities the duties of the city engineer are more usually those of a strictly technical character, while an official under the title of master of works has similar duties to those of the city surveyor in England. In the French cities road control is also under a municipal elective body, but the engineering organization with its various divisions in control of the different branches of municipal activity is much more scientifically worked out, without so much regard to historic precedent as prevails in Great Britain; although it seems, judging from results, that the simpler organization and illogical arrangement frequently prevailing in Great Britain is more efficient. Germany being an imperial federation of many different governments presents no fixed rule or system which its different cities follow, except that in all a public works department with powerful authority controls many details left to the individual in Great Britain and France, producing a very uniform and standard condition of streets throughout each municipality and regulating matters down to such details as the proper color of flowers to achieve a uniform effect in window-boxes.

Very variable practice exists in the different public works departments abroad as to the method of carrying on street construction, some cities depending entirely on direct purchase of materials and construction by the municipal organization; cthers doing all work, including maintenance repairs, by contract; and still others combining the two systems in varying degrees.

Where contracts are made their forms are also very widely different. In view of the many criticisms that have been made against long guarantee contracts prevalent in this country, it is interesting to note that this practice is quite common abroad. In order to illustrate the actual practices in different parts of Europe, it has been thought of sufficient interest to give here a series of typical contracts and abstracts of reports and specifications in some of the leading cities of Europe, which show, better than any generalized statement can, the methods employed for organization and construction.

TYPES OF PAVEMENT EMPLOYED

FOUNDATION

The use of foundation under the wearing surface of the pavement, while not a modern invention, has been used to a considerable extent only in recent times. The old Roman roads were the most conspicuous instances of pavements in ancient times with rigid foundations, but these were limited to a few main thoroughfares and were of a type not developed in city streets at the time of their construction or subsequently.

Up to the middle of the last century the pavement consisting of stone blocks laid directly on the ground surface of the street was considered satisfactory in all cities. At the present time such surface is used on a great part of the streets in every great European city. It was not until the year 1890, when was commenced the placing of electric wires in underground conduits instead of on overhead poles, followed within a few years by the introduction of motor-drawn vehicles in large numbers, that the necessity for a rigid foundation under à repairable wearing surface for city streets assumed great importance. Any argument, therefore, which is based on the assumption that there has long existed in Europe some superior method of street paving construction, including the use of a heavy rigid foundation, or that there exists there some uniform practice in the employment of a smooth non-wearing surface, has no basis in fact.

At the present time, due to the great increase in weight of traffic on the streets of cities of the first class and due to the frequent necessity for opening them for the laying of various substructures required by conditions which have arisen within the past twenty-five years, there is universal argreement among those in control of city highways that concrete foundations are indispensable when constructing new pavements in important thoroughfares. Such foundations are essential in almost all streets of American cities, which, in addition to having been disturbed for subsurface construction, are very largely on regraded ground; whereas many of the older cities of Europe have streets which have occupied their present position for hundreds of years and where, as can be seen in Hamburg in the case of a street not subject to frequent opening, the stone block surface can be satisfactorily maintained on the original hard soil underlying it. Subsurface conditions in London, on the other hand, are due to the nature of the underlying material, such as to justify the authorities there in demanding the heaviest foundations to be found anywhere, 12 inches being usual in the central portion of the city. But even in London there was found in the outlying residence districts a large proportion of satisfactorily surfaced streets without foundation.

Great differences exist as to the thickness of foundation where used and the proportioning of materials composing them. Four-inch concrete is regarded as satisfactory in many places, even in such an important city as Brussels. Probably the standard thickness at the present time is from six to eight inches.

Its' composition in different places varies between wide limits. A cheap and easy form of criticism occasionally indulged in by those well enough informed to know better is to direct public complaint against some specified case of foundation concrete work in New York, often based on the authority of some eminent engi. neer (name not given) who observed the work on his way through the street and stated that the amount of cement employed was inadequate and the materials not properly mixed to produce a durable foundation. On such criticism argument has been based that the proportioning of such concrete in Manhattan at the ratio of one of cement to three of sand and six of stone or gravel does not produce a strong enough mixture.

For purposes of comparison the following table shows some of the varying proportions abroad:

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