In 1919 he joined the Washington staff of the American Automobile Association. He served in many capacities, including editor of the Association magazine, American Motorist; Director of Roads, AAA Good Roads Board; and subsequently, Executive Chairman of the Association.
Leaving the AAA in 1925, Eldridge joined the staff of the District of Columbia government to become the first Director of Traffic for the City of Washington. At the time of his retirement on December 31, 1946, he was the Assistant Director of the D.C. Department of Vehicles and Traffic.
Eldridge was a prolific writer. Mention of only a few of his efforts will indicate the breadth of his interests in highway matters.
For the 1899 Yearbook of the U.S. Department of Agriculture he wrote on the “Progress of Road Building in the United States.” To Historic Highways of America, volume 15, entitled “The Future of Road-Making in America, A Symposium by Archer Butler Hulbert and Others,” published in 1905, he contributed Chapter III on “Good Roads for Farmers.”
He provided two articles for the Third Annual Edition (1922) of the Highways Green Book, published by the American Automobile Association. These related to “Highway Financing and Taxation” and “Accident Prevention Suggestions.” Part II of the 1925 Proceedings of the National Safety Council contains a paper by him on “Traffic Control Systems.” Also, the 1935–36 Convention Proceedings of the American Road Association includes a paper he prepared on “Should Pedestrian Traffic Be Regulated?”
