394 



SCIENCE 



[N. S. Vol. XXXIII. No. 845 



7. Sign posts shall be erected by the state high- 

 way departments to give notice of points of dan- 

 ger and to give information as to the route of the 

 road. 



Relation between Modern Traffic and the Align- 

 ment and Profile in Highway Design: H. B. 

 Drowne, Providence, R. I. 



Preliminary to designing a road, a careful 

 study should be made of the existing traffic con- 

 ditions and those to be expected, since there are 

 several features in the design that depend upon 

 whether a road is to serve only a horse-drawn 

 vehicle traffic, a combination horse-drawn vehicle 

 and motor-car traffic or a motor-car traffic alone. 

 Wider roads are required where there is much 

 motor-car traffic and on important roads a min- 

 imum width of twenty feet, is advocated. Also 

 the transverse slope or crown of the road should 

 be made from one fourth inch to one half inch 

 per foot. Sharp curves are not detrimental to a 

 road that takes mostly a horse-drawn vehicle 

 traffic, but if a heavy motor-car traffic is expected 

 all bad curves should be eliminated or reduced 

 as much as possible, since they are not only 

 expensive to maintain but are also extremely 

 dangerous. Moreover, the curves should have a 

 one-way slope up from the inside edge, as this 

 will distribute the wear more evenly over the 

 entire width of the road. There is no need of 

 reducing the maximum grades now in common use 

 on the improved roads. 



The Present Status of the Use of Bituminous 

 Materials in the Construction and Maintenance 

 of Soads in the United States: A. H. Blan- 

 CHAED, Brown University. 



As an indication of the development of the use 

 of bituminous materials in road construction and 

 maintenance, statistics are submitted based on 

 tne work accomplished by the state highway 

 departments of Maine, Maryland, Massachusetts, 

 New Hampshire, New Jersey, New York and 

 Rhode Island. The total amounts of bituminous 

 work in the various years are as follows: 1908, 

 350,000 sq. yds.; 1909, 7,750,000 sq. yds.; 1910, 

 18,000,000 sq. yds. 



The most notable developments have been : ( 1 ) 

 In the increased use of liquid asphalt and heai-y 

 asphaltic oils for surface treatment as is shown 

 by the following figures, 1908, 208,000 sq. yds.; 

 1910, 2,434,000 sq. yds. (2) In the increased 

 use of light oil as a dust layer, as is indicated 

 by its non-employment in 1908, while 9,825,000 

 sq. yds. were treated in 1910. (3) The extensive 

 use of asphalts, solid at ordinary temperatures, 

 or combinations of asphalt and tar in connection 



with the penetration method of constructing bi- 

 tuminous pavements, the total square yards built 

 in 1910 being 4,400,000 sq. yds., while no work of 

 this character was done in 1908. (4) The in- 

 crease in the use of liquid asphalts and heavy 

 asphaltic oils in the construction of bituminous 

 pavements by the mixing method, as is shown by 

 the following figures, 1908, 3,000 sq. yds.; 1909, 

 151,000 sq. yds., and in 1910, 335,000 sq. yds. 



Also attention is called to the more general use 

 of refined tar in place of crude tar, the increased 

 use of mechanical distributors both in the surface 

 treatment of old roads and the construction of 

 bituminous pavements by the penetration method 

 and the introduction of mixing machines in con- 

 nection with the construction of bituminous pave- 

 ments by the mixing method on state highway 

 work. 



Certain Considerations affecting the Selection of 

 Bituminous aiuL Mineral Matter for Road Con- 

 struction and Surface Treatment: J. C. Tea- 

 villa, St. Louis, Mo. 



Highway engineers are giving much attention 

 to the investigation of bitumens and to the devel- 

 opment of specifications for bituminous materials, 

 but in the opinion of the writer insufficient atten- 

 tion is paid to the study of the mineral aggregate. 

 The life of an asphalt or bitulithic pavement has 

 been shown to depend upon the character of the 

 aggregate to a great extent, and in the case of 

 bituminous concrete or a bituminous wearing 

 surface the same is true. 



In general mineral dust is as objectionable as 

 moisture in the construction of bituminous roads. 

 The wearing qualities of the mineral matter 

 employed affect the life of a road and also the 

 form of construction. In the case of a very soft 

 stone better results ensue when the larger stone 

 is placed on top. 



The writer's experience proves to him that 

 resiliency in the surface is of importance in 

 lengthening the life of a road or pavement. Bi- 

 tumens should, therefore, not be brittle at low 

 temperatures nor should they be too soft at high 

 temperatures. St. Louis has specifications gov- 

 erning the special adaptability and the methods 

 of application for surface treatment of four 

 grades of oil. 



Care should be taken to keep oiled streets clean. 

 The oiling of all road intersections is important 

 in this connection. 



Need of and the Opportunity for Technically- 

 trained Men in Highway Work: A. N. John- 

 son, Springfield, 111. 

 Tliis paper reviews briefly the history of road 



