quicken

To quicken a curve means to reduce its radius, making it turn more sharply. On a road, ramp, or channel, quickening increases the rate of directional change per unit of distance. A gentle arc with a 100-meter radius might be quickened to 50 meters, forcing traffic or flow to change direction twice as abruptly. The term also applies to grades: quickening a slope means increasing its angle to the horizontal, so a 5 percent grade becomes 8 percent, say.

In road design and earthmoving, quickening a horizontal curve typically requires widening the surface (superelevation) to counteract centrifugal force and prevent skidding. Vertical curves are quickened by steepening, which affects drainage, sight distance, and the strength required from fill or subgrade. Channels, ditches, and waterways may be quickened to accelerate flow, though this increases erosion risk and hydraulic stress.

The word quicken, meaning to make fast or accelerate, describes what happens to an object's rate of directional or vertical change as the curve or incline tightens. The term is now largely replaced by more precise modern language: engineers say reduce radius, increase grade, or steepen rather than quicken. However, the word survives in older contracts, survey notes, and established practice in some regions, particularly in Britain and Commonwealth countries.

Quickening a curve or grade is not a routine adjustment; it affects load capacity, safety, cost, and environmental impact. Tighter horizontal curves demand stronger pavement, wider rights-of-way, and increased maintenance. Steeper grades increase runoff, reduce trafficability for heavy vehicles, and raise foundation and retaining costs. These trade-offs mean quickening is a deliberate design decision, not casual fine-tuning.