DESIGN PROBLEM $1$

A divided rural multilane highway is required to cope with a given AADT $3350.$ A $60$

mi$/$h design speed is chosen with lanes of a standard $3\mathrm{.}36$ m width and

obstructions within $1\mathrm{.}22$ m on both sides of roadway. The terrain is rolling

and the percentages for the various heavy vehicle types are as follows:

PT $=6\%,$ PB $=6\%$ and PR $=5\%.$ The Driver Population is $$Ideal$.$ The

Peak Hour Factor $($PHF$)$ is $0\mathrm{.}85$ and the Directional Factor D is estimated

at $0\mathrm{.}6.$

The client is required to design based on high performance and

sustainability requirements. In detail, the highway is required to maintain

LOS B and it is to be designed to cope with the $30$th highest hourly volume

during the year.

Provide step$-$by$-$step calculations and critically motivate the followings:

$1\mathrm{.}1.$ The number of lanes in each direction.

$1\mathrm{.}2.$ If the client requires a reduction of $1$ lane per direction,

demonstrate what is the best solution to adopt between a$)$

extending the $$Distance to obstruction from travelled edge$$ up to

$1\mathrm{.}83$ m or greater, or b$)$ rearranging the whole highway over a type

of terrain from $$rolling$$ to $$level$.$ Critically discuss and justify the

obtained results and indicate which option is more sustainable and

why.

$1\mathrm{.}3.$ To support sustainability of the project, discuss potential solution$($s$)$

$($also in combination$)$ other than those at point $1\mathrm{.}2,$ that may reduce

number of lanes for the concerning highway. Based on the

competent Highway Authority, the following parameters cannot be

varied: divided multi$-$lane arrangement; AADT; Design Speed $=60$

mi$/$h; $$ideal$$ driver population; PHF $=0\mathrm{.}85$; D $=0\mathrm{.}6.$

Provide step$-$by$-$step calculations to prove your point and rank the

found solutions from the most to the less sustainable, including

providing critical comments to justify your answer