There may be stretches of road where the safe overtaking distance can not be provided. In such case, overtaking opportunity for vehicles moving at a design speed should be given at frequent interval. These zones which are meant for overtaking, are called overtaking zones.
Minimum length of overtaking zone should be three times the safe overtaking distance i.e, 3(d1+d2) for one way traffic & 3(d1+d2+d3)for two way traffic.
[O.S.D = Overtaking Sight Distance ]
O.S.D =(d1+d2) for one way traffic=(d1+d2+d3) for two way traffic.
SP1 = Sign Post ” Overtaking zone ahead”
SP2 = Sign Post “End of Overtaking zone”