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## Overtaking Or Passing Sight Distance

The minimum sight distance needed by a driver on a two-way road to be able him to overtake another vehicle ahead with safety against the traffic from the opposite direction is called overtaking sight distance or say passing sight distance.

### Factors Affecting on Minimum Overtaking Sight Distance

The minimum overtaking sight distance depends upon the following factors:

- Speed of the overtaking, overtaken and the vehicle coming from the opposite direction.
- Rate of acceleration of the overtaking vehicle.
- Spacing between the vehicle.
- Skill and reaction time of the driver.

### Analysis of Overtaking Sight Distance

Let, = Distance travelled by the overtaking vehicle ‘A’ during the reaction time t sec of the driver from position A1 to A2.

= Distance travelled by the overtaking vehicle ‘A’ from position A2 to A3 during the actual overtaking operation, in time T sec.

= Distance travelled by the on coming vehicle ‘C’ from position C1 to C2 during the actual overtaking operation of A, in time T sec.

= Speed of the overtaken vehicle in m/sec. S = Minimum spacing between vehicle A and B.

Thus, = . t

The minimum spacing (S) between the vehicle is given by the empirical formula:

S = (0.7 + 6) m

The distance covered by the overtaken vehicle B from position B1 to B2 during the overtaking operation in T sec is given by,

b = .T

= 2S + b = .T + aT**²**/2 Where ‘a’ is acceleration of the vehicle A in m/Sec

Or, T = √ (4S/a)

Hence, = 2S + .T & = V.T

Where V is the design speed of vehicle C in m/Sec

### Overtaking Sight Distance Formula For Two way Traffic

Thus, for two way traffic overtaking sight distance(O.S.D) =

= ( .t + 2S+ .T + V.T) m

### Overtaking Sight Distance Formula For One way Traffic

Thus, for one way traffic overtaking sight distance(O.S.D) = +

= ( .t + 2S+ .T ) m

If is not given then its value may be assumed as = (V – 4.5) m/Sec, Where V is the design speed in m/Sec.

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