American Railway Engineering Association (AREA) was formed in 1899 as a forum for the development and study of recommended practices for the newly-integrated standard-gauge North American railway network. The AREA dealt with the many engineering challenges through standing technical committees. The AREA issued its first Manual of Recommended Practices in 1905.
The AREA was merged into the American Railway Engineering and Maintenance-of-Way Association (AREMA) in 1997 along with three other railway engineering associations.
About the AREA 10-Chord Spiral
The AREA 10-Chord Spiral was adopted in North America early in the 20th century. Spirals were calculated without computers from tables. Now we can plug the formulas into a computer program or spreadsheet and make the calculation instantly. We can use any convenient number of chords, or stations along the spiral.
Material on the Definitions, Notation, and Formulas tabs is quoted directly from an old C. & N. W. RY. Engineering Department booklet STANDARD 10 CHORD INSTRUMENT SPIRAL (A. R. E. A.) which itself quoted from a full AREA document. No year given.