(Solved): A two-lane highway has a posted speed limit of \( 80 \mathrm{Km} / \mathrm{h} \) on the horizontal ...

A two-lane highway has a posted speed limit of \( 80 \mathrm{Km} / \mathrm{h} \) on the horizontal section, as shown. A recent daytime crash (driver traveling eastbound and striking a stationary roadway object) resulted in a fatality and a lawsuit alleging that the \( 80 \mathrm{Km} / \mathrm{h} \) posted speed limit is an unsafe speed for the curve in question and was a major cause of the crash. The horizontal sightline offset \( \mathrm{C}=10 \mathrm{~m} \). Coefficient of lateral friction is \( 0.12 \). Perception-reaction time is \( 2.5 \mathrm{sec} \), and \( f=0.35 \). The stations of \( P C \) and \( P T \), intersecting angle, and superelevation rate (e) are all given (see drawing). Each station is \( 30 \mathrm{~m} \). 1- Determine the radius of the horizontal curve. 2- Based on the design speed ( \( 80 \mathrm{Km} / \mathrm{h} \) ), determine the minimum sightline offset (C) that can be allowed. 3- Based on the design speed \( (80 \mathrm{Km} / \mathrm{h}) \), determine the minimum superelevation rate (e) that can be used. 4- Evaluate and comment on the posted speed limit (safe or unsafe and why?). Note: Tables from AASHTO and GDGCR are NOT allowed in solving this question. \( \mathrm{P} \)