Overtaking Sight Distance
Overtaking Sight distance is minimum distance required by vehicle moving at design speed to overtake the vehicle moving at slower speed safely against the another vehicle coming from opposite direction. It depends upon following factors:
Vehicle A travelling at design speed has to overtake vehicle B on two way traffice lane when third vehicle C comes from opposite direction.
d1= distance travelled by overtaking vehicle A during the reaction time 't' sec ot position of driver A from A1 to A2.
d2= distance travel by vehicle A from position A2 to A3 during the actual overtaken operation within time 'T'.
d3= distance travlled by vehicle C from position C1 to C2 during overtaking operation of vehicle A.
Vehicle A travel at design speed= v m/sec
Vehicle B moves at speed = vbm/sec
(If speed of vehicle B is not given, then take vb= v- 4.5 m/sec or Vb= V-16 Km/hr)
Vehicle C moves at design speed= v m/sec
If A2B1= B2A3 = s, minimum spacing distance between two vehicles where
s = 0.7vb+6 (m).
A2A3= d2 but A2A3= s+b+s
.: d2=b+2s.
It may be assumed that vehicle A is forced to reduce speed to vb and move behind vehicle B with clear spacing s till there is opportunity to over taken the vehicle B.
The distance travelled by vehicle A during reaction time is d1,
Therefore
d1=vb×t.
From A2, vehicle start accelerate and start overtaking the vehicle B and then comes back into same line at A3.
A2A3=d2.
d2=vb×T + 1/2 × a ×T×T
Where a= acceleration which is given by following table
But d2= b+2s
While comparing both equation,
b=vb×T and 2s=1/2 ×a×T×T
During overtaking operation, vehicle C moves at design speed v cover the distance= d3= v×T.
Total overtaking distance=d1+d2+d3.
If the road is single side traffic lane then there is no vehicle C that comes into opposite direction. Thus d3 is neglected.
Then total overtaking sight distance= d1+d2.
Safe Overtaking sight distance = 5* total overtaking distance calculated when there is no restriction of land. (OR)
= 3* total overtaking sight distance when there is restriction of land.
Overtaking Sight distance is minimum distance required by vehicle moving at design speed to overtake the vehicle moving at slower speed safely against the another vehicle coming from opposite direction. It depends upon following factors:
- Speed of overtaking vehicle ( v m/s)
- Speed of overtaken vehicle ( vb m/s)
- Speed of opposite vehicle ( v m/s)
- Reaction time of overtaking vehicle driver
- Spacing between the vehicles (s)
- Acceleration of overtaking vehicle (m/s2)
- Gradient of the road
Vehicle A travelling at design speed has to overtake vehicle B on two way traffice lane when third vehicle C comes from opposite direction.
d1= distance travelled by overtaking vehicle A during the reaction time 't' sec ot position of driver A from A1 to A2.
d2= distance travel by vehicle A from position A2 to A3 during the actual overtaken operation within time 'T'.
d3= distance travlled by vehicle C from position C1 to C2 during overtaking operation of vehicle A.
Vehicle A travel at design speed= v m/sec
Vehicle B moves at speed = vbm/sec
(If speed of vehicle B is not given, then take vb= v- 4.5 m/sec or Vb= V-16 Km/hr)
Vehicle C moves at design speed= v m/sec
If A2B1= B2A3 = s, minimum spacing distance between two vehicles where
s = 0.7vb+6 (m).
A2A3= d2 but A2A3= s+b+s
.: d2=b+2s.
It may be assumed that vehicle A is forced to reduce speed to vb and move behind vehicle B with clear spacing s till there is opportunity to over taken the vehicle B.
The distance travelled by vehicle A during reaction time is d1,
Therefore
d1=vb×t.
From A2, vehicle start accelerate and start overtaking the vehicle B and then comes back into same line at A3.
A2A3=d2.
d2=vb×T + 1/2 × a ×T×T
Where a= acceleration which is given by following table
But d2= b+2s
While comparing both equation,
b=vb×T and 2s=1/2 ×a×T×T
During overtaking operation, vehicle C moves at design speed v cover the distance= d3= v×T.
Total overtaking distance=d1+d2+d3.
If the road is single side traffic lane then there is no vehicle C that comes into opposite direction. Thus d3 is neglected.
Then total overtaking sight distance= d1+d2.
Safe Overtaking sight distance = 5* total overtaking distance calculated when there is no restriction of land. (OR)
= 3* total overtaking sight distance when there is restriction of land.
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