Design of horizontal and vertical alignments, super elevation, sight distance and grades, is worst affected by
- Awidth of the vehicle
- Blength of the vehicle
- Cheight of the vehicle
- Dspeed of the vehicleCorrect
Solution
Concept
Factor affecting highway geometric design
Formula
NONE
Step-by-step solution
1. Geometric design elements include horizontal/vertical alignments, superelevation, sight distance, and grades. 2. Vehicle speed directly influences dynamic forces, stopping distances, and sight requirements as a squared variable in formulas. 3. Therefore, the speed of the vehicle is the primary factor that worst affects these geometric design parameters. Answer: D
Explanation
Vehicle speed directly governs required stopping sight distances, horizontal curve radii, superelevation rates, and vertical alignments. Higher speeds demand much larger geometric dimensions to safely maintain vehicle stability and driver reaction time. Because speed affects almost every design parameter, it is the primary factor influencing geometric alignment.
Why the other options are wrong
A) Width of the vehicle primarily affects the width of pavement lanes and shoulders. B) Length of the vehicle mainly influences extra widening on curves and minimum turning radius. C) Height of the vehicle primarily affects the vertical clearance of underpasses and overhead structures.
Shortcut
Vehicle speed is the primary driver of all geometric design features.
Common mistake
Assuming physical dimensions like vehicle length or width affect geometric design elements more than speed.
Correct answer: D) speed of the vehicle