2 BULLETIN 249, IT. S. DEPARTMENT OF AGRICULTURE. 



to 1909 the total area of concrete pavements which had been con- 

 structed in this country was comparatively small, and in the majority 

 of cases these pavements were frankly regarded as experiments. 

 During 1909 the road officials of several communities concluded that 

 the results already obtained were sufficiently encouraging to warrant 

 them in undertaking the construction of concrete roads on a larger 

 scale, and since that time many such roads have been completed. 

 Wayne County, Mich., was one of the first communities to adopt this 

 form of construction and at present probably has a greater mileage 

 of roads paved with concrete than any other county in the United 

 States. 



The fact that the majority of the concrete pavements which have 

 been constructed have proved entirely satisfactory where traffic con- 

 ditions were not unduly severe is serving to increase their popularity 

 very rapidly. This is evidenced by the following tabulation, showing 

 the approximate number of square yards of such pavements that have 

 been constructed in the United States each year beginning with 1909 : 



Square yards. 



1900 364, 000 



1910 850, 000 



1911 1, 800, 000 



1912 6, 470, 000 



1913 10, 100. 000 



1914 (estimated) 19, 200, 000 



Enthusiastic advocates of concrete roads should bear in mind that 

 such roads can never be economically adapted to all traffic conditions, 

 and those who are in responsible charge of road-improvement work 

 should realize the importance of making a careful economic compari- 

 son of the various kinds of road surfaces under the conditions to be 

 met before deciding upon the type of improvement to adopt. 



The principal advantages which concrete pavements possess may 

 be briefly stated and commented upon as follows : 



1. As far as can be judged, they are durable under ordinary subur- 

 ban and rural traffic conditions. While it is true that there are no 

 very old concrete pavements in existence, the present condition of 

 many of those which have undergone several years' service would 

 seem to warrant the above statement. 



2. They present a smooth, even surface, which offers very little re- 

 sistance to traffic. In the past the surfaces of concrete pavements 

 have sometimes been roughened in order to insure a good foothold 

 for horses. This practice has now been abandoned, except on wrv 

 steep grades, because it tends greatly to accelerate deterioration of 

 the pavement, and because the smooth surface has been found to 

 afford a fairly satisfactory foothold under all ordinary conditions. 



3. They produce practicall}' no dust and may be easily cleaned. 



