BUREAU OF PUBLIC ROADS. 467 



types, the only condition being that the type selected shall be con- 

 sistent with the traffic requirements under the climatic and soil con- 

 ditions prevailing. 



The division of the roads of the system into primary and secondary 

 classes does not imply tliat all roads of the primary class are to be 

 surfaced with a higher type of material than the secondary roads. 

 On the contrary, it is to be anticipated that primary roads in some 

 sections of the country, notably in many of the Southern and Western 

 States, will not require a higher type of surface than the secondary 

 roads in other sections— for example, New England and the industrial 

 East. 



In many instances it has bee« found advisable to grade and drain 

 a road and delay an expensive pavement untij a later time. This 

 policy will be continued under the same conditions; that is, when 

 the volume of traffic at the time of original construction is not large 

 enough to require any better surface than can be built of selected 

 soil, sand-clay, or gravel, when financial considerations require that 

 the expense of a pavement be deferred, and when, as in the light of 

 past experience it has often been found advisable, a delay to allow 

 the subgrade to become stable is believed to be necessary. In such 

 cases the plan will be, as it has been in the past, to so design and 

 construct the grades and drainage structures and whatever tem- 

 porary surfacing that is applied, that any additions or subsequent 

 improvements can be made without loss of prior investment. 



The increasing number of accidents at highway grade crossings 

 has become a matter of grave concern, and has led to the adoption 

 of a policy looking to the elimination of such dangerous crossings 

 wherever practicable on Federal-aid roads. The policy, which has 

 met with the generous support of the States, is that all existing 

 grade crossings on the Federal-aid highway system shall be classified 

 for priority of elimination by agreement between the bureau and 

 the State highway departments, and the improvements shall be 

 carried out as rapidly as practicable. 



ORGANIZATION CHANGES. 



Changes in the organization during the year have been relatively 

 unimportant. The most important was a reduction in the number 

 of field districts from 13 to 12. One district engineer resigned to 

 accept a position as a State highway engineer at considerable 

 increase in salary. 



In general, the personnel turnover during the year was less than 

 in the two or three years previous and involved the loss of fewer 

 of the bureau's more valuable employees. 



The following table shows the relation of the turnover during 

 1922 to that of the previous year: 



District engineers , 



Engineers of senior highway grade. 



E ngineers of highway grade , 



Engineers of junior grade 



Clerks 



1922 



1 



11 



4 



1 



28 



