A two$-$lane highway $(12-$ft lane in each direction$)$ goes from normal crown with $2\%$ cross slope

to full superelevation by means of spiral transition curve. The following information is

provided: emax $=10\%,$ design speed $=50$ mph$,$ radius of curvature is $840$ ft$,$ SC station is @ $12+$

$00,$ and length of circular curve is $1580$ ft$.$ Using the design principles of the AASHTO Green

Book, determine the following:

a$.$ The most appropriate length of the transition spiral curve.

b$.$ Determine the superelevation transitions going into and out of the circular horizontal curve