COMMUNICATION AND TRANSPORTATION 263 



these death-traps should never be overlooked. The cost of this 

 work will form no small part of our future highway disburse- 

 ments. Even when elimination is impossible, much may be done 

 to decrease danger at crossings. 



As to pavements, for minor roads this will always depend on 

 the relative costs of locally available materials. Gravel, oyster- 

 shells, and macadam will probably always be able to provide for a 

 considerable mileage of the lesser roads. Macadam with a 

 blanket coat of tar or asphalt, well maintained, will carry a con- 

 siderable traffic, but only at a fairly high maintenance cost. For 

 more important roads Portland cement concrete and bitumi- 

 nous concretes seem the most promising solution. Block pave- 

 ments, brick, wood, asphalt block, and granite on a concrete base 

 will be required for the heaviest traffic and for such grades on 

 bituminous concrete roads as may be found too steep for that 

 material. 



Roads must be designed for the speed and weights that will 

 be used on them. Whether there be a statutory speed limit or 

 not, it is not seriously regarded and will in time probably dis- 

 appear. Any prudent designer to-day will count on not less 

 than forty miles. There is little use in providing a surface suited 

 for such a speed without giving the corresponding widths and 

 curvatures. Without knowledge of weights to be carried, bridge 

 design is but guesswork. Pavements and foundation courses 

 must be suited to the weights to be carried. These should be 

 regulated by legislation uniform in all the States. The paved 

 way for important roads should not be less than eighteen feet on 

 tangents ; curves should have radii of not less than 1,000 feet with 

 increased widths of paved surface. 



Grades -are a matter of both economy and safety; with 

 Bituminous surfaces anything in excess of five per cent, becomes 

 too slippery for horses ; automobiles also skid dangerously thereon. 



Many of the minor appurtenances of our roads deserve and 

 should receive more thorough study than has generally been 

 given them. Road signs, for example, should be legible from 

 whatever side approached. Running beyond a sign before being 

 able to read it destroys, to a great extent, its usefulness and is a 

 source of actual danger. Dust in excessive quantities is not only 

 a nuisance, but has become a serious danger. 



