a$)$ What are the initial grade and final grade of the vertical curve?

b$)$ Based on the AASHTO design standard, what is the maximum safe speed for this section $($both

directions$)?$

A $3km$ curved section of an expressway in an urban area is characterized by a radius of $650m($to the

centreline of the road$).$ According to the MTO study on provincial highway volumes in $2016,$ the

estimated AADT of this section is $111,200$ vehicles$/$day$.$ The highway is a six$-$lane divided highway

with a posted speed of $100k\frac{m}{h}$ and a maximum superelevation of $0\mathrm{.}06.$ The width of each travelled

lane is $3\mathrm{.}75m$ and the width of the median is $3m.$ This section is mainly in a fill area with a slope of $5$:$1$

in the clear zone.

a$)[7$ marks$]$ Would you consider that the radius of this curve is safe?

b$)[7$ marks$]$ What length of the spiral curve between the tangent sections and the circular curve

would you recommend?

c$)[6$ marks$]$ What is the recommended width of the clear zone $($CZ$)$ at the outer side of the

travelled roadway?