In the preparation of American Rural Highways reference was had to many books on highway subjects and to current periodical literature. Wherever direct extracts were made from such source, appropriate acknowledgment appears in the text. T. R. AGG AMES, IOWA, AUGUST 18, 1920. CONTENTS PREFACE vii CHAPTER I THE PURPOSE AND UTILITY OF HIGHWAYS Transportation Problem--National in Scope--Development in Traffic--Location or Farm to Market Traffic--Farm to Farm Traffic--Inter-City Traffic--Inter-County and Inter-State Traffic--Rural Education--Rural Social Life--Good Roads and Commerce 1-12 CHAPTER II HIGHWAY ADMINISTRATION Township Administration--County Administration--State Administration--Federal Administration--Special Assessments--Zone Method of Assessing--General Taxation--Vehicle Taxes--Sinking Fund Bonds--Annuity Bonds--Serial Bonds--Comparison of Methods of Issuing Bonds--Desirability of Road Bonds 13-28 CHAPTER III DRAINAGE OF ROADS The Necessity for Drainage--Importance of Design--Surface Drainage--Run-off--Ordinary Design of Ditches--Underground Water--Tile Drains--Lying Tile--Culverts--Length of Culvert-- Farm Entrance Culverts--Metal Pipe--Clay and Cement Concrete Pipe--Concrete Pipe--Endwalls for Culverts--Reinforced Concrete Box Culverts--Drop Inlet Culverts 29-41 CHAPTER IV ROAD DESIGN Necessity for Planning--Road Plans--Problems of Design-- Preliminary Investigations--Road Surveys--Alignment-- Intersections--Superelevation--Tractive Resistance--Rolling Resistance--Internal Resistance--Air Resistance--Effect of Trades--Energy Loss on Account of Grades--Undulating Roads-- Guard Railing--Width of Roadway--Cross Section--Control of Erosion--Private Entrances--AEsthetics 42-62 CHAPTER V EARTH ROADS Variations in Soils--Variation in Rainfall--Cross Sections Elevating Grader--Maney Grader--Slip Scraper--Fresno Scraper--Elevating Grader Work--Use of Blade Grader-- Costs--Maintenance--Value of Earth Roads 63-73 CHAPTER VI SAND-CLAY AND GRAVEL ROADS The Binder--Top-soil or Natural Mixtures--Sand-clay on Sandy Roads--Sand-clay on Clay or Loam--Characteristics--Natural Gravel--The Ideal Road Gravel--Permissible Size of Pebbles-- Wearing Properties--Utilizing Natural Gravels--Thickness of Layer--Preparation of the Road--Trench Method--Surface Method--Maintenance 74-88 CHAPTER VII BROKEN STONE ROAD SURFACES