Highway design — safe overtaking sight distance at V = 100 km/h For a two-lane highway with design speed 100 km/h, estimate the safe overtaking sight distance (assume representative overtaking acceleration a ≈ 0.53 m/s^2 and standard IRC assumptions for perception and clearance). Choose the closest value.

Introduction / Context:
Overtaking sight distance (OSD) on two-lane two-way highways ensures that a driver can pass a slower vehicle and return to the lane without conflict with an opposing vehicle. OSD grows rapidly with speed and depends on available acceleration.

Given Data / Assumptions:

• Design speed V ≈ 100 km/h (27.78 m/s).
• Typical overtaking acceleration a ≈ 0.53 m/s^2.
• Standard IRC-style components: initial reaction/decision, overtaking maneuver, and safety clearance with an opposing vehicle.
• Level terrain and typical traffic mix.

Concept / Approach:
OSD is the sum of distances: OSD = d_react + d_overtake + d_clear. With higher V and modest a, the overtaking time is relatively long, and the clearance portion for the opposing vehicle adds substantially to the total. For V around 100 km/h, IRC tables and derived computations place OSD in the ~700–750 m range.

Step-by-Step Solution:
Convert speed: V = 27.78 m/s.Approximate overtaking time using kinematics with acceleration a and speed differential typical of design practice (leading to 10–12 s maneuver time).Compute distance travelled by the overtaking vehicle during decision and maneuver plus the distance covered by the opposing vehicle during the critical interval.Sum components → OSD ≈ 700–750 m; adopt the conservative value given.

Verification / Alternative check:
IRC guideline values for 100 km/h corroborate an OSD of roughly three-quarters of a kilometre. Lower figures (300–470 m) align with lower design speeds (60–80 km/h).

Why Other Options Are Wrong:
300–320 m: Suitable for ~60 km/h. 470–560 m: Near values for ~80–90 km/h. 750 m matches 100 km/h design requirements.

Common Pitfalls:

• Equating OSD with stopping sight distance (SSD); OSD is much larger.
• Ignoring opposing-vehicle movement during the maneuver.

Final Answer:
750 m