Length of Summit Curve Design Method - Civil Engineering

## Length of Summit Curve

The length of summit curve is designed based on the two criteria:
i) Considering the stopping sight distance .
ii) Considering the safe overtaking sight distance or intermediate sight distance.
 Length of Summit Curve

### i)Considering the Stopping Sight Distance

The length of summit curve(L) according to this criteria may be determined for the two conditions
a) When the total length of summit curve (L) is grater than the stopping sight distance(S)
b) When the total length of summit curve (L) is less than the stopping sight distance.

When the total length of summit curve (L) is grater than the stopping sight distance, the value of L(length of summit curve) is calculated from the following equation:
L = NS/(√2H + √2h)2
Where,
H = is the height of eye level of driver above roadway surface in m.
h = is the height of subject above the pavement surface in m and N is the deviation angle.

When the total length of summit curve (L) is less than the stopping sight distance, the value of L(length of summit curve) is calculated from the following equation:
L = 2S - (√2H + √2h)/N

### ii) Considering the safe overtaking sight distance or intermediate sight distance

The length of summit curve(L) according to this criteria may be determined for the two conditions
a) When the total length of summit curve (L) is grater than the overtaking or intermediate sight distance (S) .
b) When the total length of summit curve (L) is less than the overtaking or intermediate sight distance (S) .

When the total length of summit curve (L) is grater than the overtaking or intermediate sight distance (S) ,the value of L is calculated from the following equation:
L = NS2/8H

When the total length of summit curve (L) is less than the overtaking or intermediate sight distance (S),the value of L is calculated from the following equation:
L = 2S - 8H/N