ROADS 



179 



Large Bridges. All large bridges should be designed and 

 their construction supervised by a skilled engineer. In the 



Figr. 98. A concrete bridge which failed on account of the foundation. 



majority of states the state highway commission is in a posi- 

 tion to furnish such an engineer. 



QUESTIONS 



1. Why should culvert and bridge construction receive careful 

 consideration? 



2. What should be considered in selecting a culvert or bridge? 



3. What should govern the size of the culvert? 



4. Why is it important to have good bridge foundations? 



5. Why is concrete a good material for culverts and bridges? 



6. What are the merits of metal culverts? 



7. What is the work of the State Highway Commission? 



REFERENCE TEXTS 



Roads and Pavements, by I. O. Baker. 



Highway Construction, by Austin T. Byrne. 



A Text-book on Roads and Pavements, by Frederick P. Spaulding. 



Bulletins of the Office of Public Roads, U. S. Depart, of Agric. 



