LECTURE 5: SUPERELEVATION
Barnett sought to improve the alignment of roads by keeping
tangents to a minimum and inserting superelevation throughout the
transition curve. In that way the physics of the moving vehicle
would be distributed throughout the spiral from the tangent to full
curvature. He used the spiral developed by Searles for railroads
which was based on ten compound curves except that Barnett used
chords to simplify staking the spiral in the field. All of Barnett's
tables, therefore, incorporate superelevation and transition based
on the Ten Chord Spiral. Survey crews stake out centerline and
edge of pavement directly from the tables.
