Correct Answer - Option 3 : 50 Km/hr
Concept:
Design Speed of Roads:
- Design speed is defined as the highest continuous speed at which individual vehicles can travel with safety on the highway when weather conditions are conducive.
- Design speed is the single most important factor that affects geometric design.
- It directly affects the sight distance, horizontal curve, and the length of vertical curves.
- Since the speed of vehicles varies with the driver, terrain, etc, a design speed is adopted for all the geometric designs.
Design Speed of Roads according to IRC given in the following table:
Road
Classification
|
Design Speed(km/hr) |
Plain |
Rolling |
Mountainous |
Steep |
Ruling |
Min |
Ruling |
Min |
Ruling |
Min |
Ruling |
Min |
Expressways |
120 |
100 |
100 |
80 |
80 |
60 |
80 |
60 |
NH and SH |
100 |
80 |
80 |
65 |
50 |
40 |
40 |
30 |
MDR |
80 |
65 |
65 |
50 |
40 |
30 |
30 |
20 |
ODR |
65 |
50 |
50 |
40 |
30 |
25 |
25 |
20 |
VR |
50 |
40 |
40 |
35 |
25 |
20 |
25 |
20 |
Where NH - National Highway, SH - State Highway, MDR - Major District Road, ODR - Other District Road, VR - Village Road
Hence, The ruling design speed for National Highways in mountainous terrain is 50 km/hr.