1.  The important factor considered in the design of summit curves on highways is __.

A. comfort to passenger

B. superelevation

C. sight distance

D. impact factor


Answer: C   sight distance





When a fast-moving vehicle travels along a summit curve, the centrifugal force will act upward, against gravity, which relieves some of the pressure on the tyres and suspension springs of the vehicle.


Thus, there is no issue with passengers feeling uncomfortable when riding on summit curves. The provision of sufficient sight distance is the only challenge in constructing summit curves.


Every portion of the road system, as well as summit curves, should always have the stopping sight distance or the absolute minimum sight distance.



2.  The ideal form of curve for the summit curve is ____.

A. lemniscate

B. circular

C. spiral

D. parabola


Answer: B circular





The sight distance is constant throughout the length of the circular summit curve. In practice, we employ square parabolic curves since they are simple to compute and provide comfortable riding.



3. Transition curves are provided on the approach to horizontal curves in order to __.

A. reduce jerk to allowable levels

B. increase jerk to allowable levels

C. minimize the length of the horizontal curve

D. simplify the laying out and construction of the horizontal curve


Answer: A   reduce jerk to allowable levels





The radius of the transition curve reduces from infinity at the point of intersection to the desired radius of the circular curve.

A automobile travelling on a straight road that curves at a radius of R experiences a sharp jerk due to the centrifugal force that suddenly acts on the vehicle just after the tangent point.

In addition to making the passengers uncomfortable, this makes it impossible to drive the vehicle safely.

The centrifugal force will gradually appear if a transition curve is added between a straight and circular curve of radius “R,” as the radius of the transition curve decreases from infinity.

The rate at which this force is introduced can be controlled by adopting suitable shape of the transition curve and by designing its length so that vehicle can have a smooth entry from the straight to the circular curve at the design speed.



4. On sag (or valley) curves the available sight distance is determined based on ___.

A. height of headlight

B. height of driver’s eye

C. height of obstacle

D. design speed


Answer: A    height of headlight




5.  At highway stretches where the required overtaking sight distance cannot be provided, it is necessary to incorporate in such sections the following ___.

A. one third of the required overtaking sight distance

B. at least twice the stopping sight distance

C. three times the stopping sight distance

D. half of the required overtaking sight distance


Answer: B   at least twice the stopping sight distance





Intermediate Sight Distance ISD = 2 * SSD

Minimum length of overtaking zone = 3 * OSD

Desirable length of overtaking zone = 5 * OSD



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