line

The line is the actual trajectory a vehicle follows as it navigates a curve or corner. It is determined by steering input, vehicle dynamics, speed, and grip, and it directly affects exit velocity and lap time. In racing and performance driving, choosing the optimal line is fundamental to speed; on public roads, it affects safety and fuel economy.

The classic racing line through a corner typically follows a geometric pattern: approach on the outside of the curve, apex at the tightest point (where the steering angle is most acute), and exit on the outside again. This path maximizes the radius of the turn and allows higher speed without losing grip. Different corners demand different lines; a hairpin requires a much tighter geometric arc than a long sweeping bend.

Vehicle setup, tire grip, and driver technique all shape what line is actually possible. A car with soft suspension and worn tires may be forced into a slower line than one with stiff springs and fresh rubber. Wet conditions force a different line than dry pavement because grip is reduced and weight transfer behaves differently. Heavy braking or acceleration on the entry or exit will alter the line because it changes the tire's load and available grip for cornering.

Running too tight an entry line (cutting toward the apex too early) causes the driver to run wide on exit and lose speed. Conversely, running too wide an entry leaves the driver too close to the inside curb at apex and forces a tight exit. Carrying too much speed into the turn, or braking too late, forces the driver to scrub speed on the entry and run a much tighter radius than intended. Trail braking, where light brake pressure continues past the turn-in point, is an advanced technique that modifies the line and can improve corner exit speed if executed correctly.

The term "line" is also used more loosely to describe any consistent path or trajectory during driving, not just through corners. Factory test drivers speak of "following the line" on a circuit when conducting durability runs or lap timing. In driver training, instructors often use trail-braking, reference points (landmarks at turn-in, apex, and exit), and repetition to teach consistent line execution.