A summit curve is formed when convexity is upward (crest formed).

Deviation angle $N$ must be positive ($N > 0$) for a summit curve.

Square parabola is standardly preferred for summit curves due to simple design and uniform rate of change of grade.

The primary design criteria for summit curves is Sight Distance (SSD and OSD/ISD), whereas headlamp sight distance is critical for valley curves.

Provides smooth vertical transition between different grades.

Ensures adequate sight distance for safe stopping and overtaking.

Prevents sudden comfort shocks to vehicle occupants.

Sight distance is restricted at the peak of the curve due to summit convexity.

Requires significant earthwork cut/fill during construction in hilly terrain.

Highway vertical alignment design at crests.

Railway track vertical gradient transitions.

Flyover crest transitions.

Option A: $+n_1$ followed by $-n_2 \implies N = (+n_1) - (-n_2) = n_1 + n_2 > 0$ (Summit Curve).

Option B: $+n_1$ followed by $+n_2$ (where $n_1 > n_2$) $\implies N = n_1 - n_2 > 0$ (Summit Curve).

Option C: Level surface ($0$) followed by $-n_2 \implies N = 0 - (-n_2) = n_2 > 0$ (Summit Curve).