Design speed = Speed of overtaking vehicle
⇒ V=90 Kmph
Speed of overtaken vehicle,
(Vb)=V−16=74 kmph
Overtaking sight distance = d1+d2
Given reaction time is 2 seconds.
∴d1=0.278×Vb×t=0.278×74×2=41.144m
d2=0.278Vb×T+2s
S=0.2Vb+6=0.2×74+6=20.8m
T=√4sa;
a=3kmph/sec=(3×518)m/s2
∴T=
⎷4×20.83×518=9.99sec
Hence,
d2=0.278×74×9.99+2×20.8
=247.11 m
∴OSD=d1+d2
=41.144+247.11
=288.254 m
Desirable length of overtaking zone
=5×OSD
=1441.27 m≃1441.5 m (say)