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The Minimum length of overtaking zone in terms of OSD as per IRC
OSD
2xOSD
3xOSD
5XOSD
3xOSD
According to the Indian Roads Congress (IRC) standards, the minimum length of an overtaking zone is defined as 3 times the Overtaking Sight Distance (OSD). This length is considered sufficient to allow a vehicle to safely overtake another vehicle moving at a slower speed on a two-lane highway.
According to the Indian Roads Congress (IRC) standards, the minimum length of an overtaking zone is defined as 3 times the Overtaking Sight Distance (OSD). This length is considered sufficient to allow a vehicle to safely overtake another vehicle moving at a slower speed on a two-lane highway.
Lmin=3×OSD — Minimum length of overtaking zone
The overtaking zone is provided on two-lane roads where OSD is not available throughout the length of the road. Providing an overtaking zone of 3×OSD ensures that even if a vehicle is in the middle of an overtaking maneuver, it has adequate distance to complete the action and return to its lane safely within the designated zone without causing a conflict with oncoming traffic.
The desirable length of an overtaking zone is 5×OSD.
The minimum length of an overtaking zone is 3×OSD.
Overtaking zones are provided on two-lane roads to enhance capacity and safety.
Overtaking zones are clearly marked with traffic signs and road markings (e.g., solid yellow lines).
Reduces accidents by providing safe overtaking opportunities.
Improves the average speed and level of service of the highway.
High initial construction cost for additional pavement width.
Requires careful geometric design and signage to prevent misuse.
Single-lane and two-lane state or national highways.
Highways traversing terrain where providing OSD throughout is economically unfeasible.
| Feature | Minimum Length | Desirable Length |
|---|---|---|
Overtaking Zone Length | 3 * OSD | 5 * OSD |
IRC also specifies that the maximum length of an overtaking zone should not exceed 5×OSD to ensure efficiency.
In cases where 3×OSD is not possible, 2×OSD is sometimes treated as the absolute minimum in restricted conditions, but 3×OSD is the standard requirement for design.
C is correct — As per IRC standards, the minimum length of an overtaking zone is 3 times the OSD.
Always remember that 3 times OSD is the minimum while 5 times OSD is the desirable length; these values are critical for geometric design questions in GATE and IES exams.