The perception-reaction time for a vehicle travelling at $90 \mathrm{~km} / \mathrm{h}$, given the coefficient of longitudinal friction of 0.35 and the stopping sight distance of $170 \mathrm{~m}$ (assume $g=9.81 \mathrm{~m} / \mathrm{s}^{2}$ ), is seconds.
The perception-reaction time for a vehicle travelling at $90 \mathrm{~km} / \mathrm{h}$, given the coefficient of longitudinal friction of 0.35 and the stopping sight distance of $170 \mathrm{~m}$ (assume $g=9.81 \mathrm{~m} / \mathrm{s}^{2}$ ), is seconds.