What are the reasons for crossing the line in an S-curve?

[DelCarmen]

The reasons for crossing the line in an S-curve: 1. The steering wheel is not straightened, causing the car to keep turning; 2. The car body leans too much to the right when turning; 3. The car body is halfway out of the line when the direction is straightened and driven away directly. Correct operation for an S-curve: There are two directions for the entrance, left entrance and right entrance. For a left entrance, the vehicle should get as close as possible to the right line before turning the steering wheel to the left; for a right entrance, the opposite applies, the vehicle should get as close as possible to the left line before turning the steering wheel to the right. When exiting the S-curve, there are two directions, left exit and right exit. For a left exit, when the front wheel just leaves, turn half a circle to the right; for a right exit, the opposite applies, when the front wheel just leaves, turn half a circle to the left.

[FaithLynn]

When I first started learning to drive, I always crossed the line in the S-curve, mainly because my vision and steering wheel coordination were poor. I only focused on the front of the car and didn’t pay attention to the wheel positions. During right turns, the left wheels easily crossed the line, and during left turns, the right wheels were at risk. The timing of straightening the steering wheel was also hard to grasp—turning too sharply or straightening too late would cause me to go off track. There was also the issue of speed; driving too fast made it impossible to adjust in time. During practice, the instructor had us drive slowly in the middle of the lane, turning the steering wheel gradually with the curve while constantly checking the rearview mirror to sense the wheel positions and make slight adjustments if they were about to cross the line. Remember not to stare at the front of the car—looking farther ahead makes it easier to judge the path.

[StKevin]

As a coach who frequently trains students, I've observed that the main issues causing the car to run over the line in an S-curve occur in three key moments: First, when entering the curve, the car body isn't properly aligned, essentially starting with the wrong angle. Second, hesitation during mid-course corrections, where the steering wheel isn't turned decisively enough when needed. The most critical moment is exiting the curve—many drivers let their guard down thinking it's almost over, only to have the rear wheels cross the line. My recommendation is to divide the S-curve into three segments during practice, using reference points for alignment in each. For instance, in the first curve, aim to have one-third of the hood cover the line; in the second curve, use the wiper node as a guide; and when exiting, pay close attention to the distance between the rear wheels and the boundary line. Avoid twisting the steering wheel like wringing a towel—instead, use the push-pull method for more precise turns.

[EvanLee]

The essence of cutting corners in an S-curve lies in insufficient anticipation and technical disconnection. Beginners often make two mistakes: first, they focus their gaze only a few meters ahead, failing to see the entire curve's trajectory; second, they steer the wheel too mechanically, counting turns like solving a math problem. I once conducted an experiment with a bicycle—on the same curve, looking into the distance naturally allows for a smooth arc, while focusing only on the front wheel inevitably leads to serpentine movement. The same principle applies to driving: scan the entire path before entering the curve, and let your hands follow your gaze, making the steering wheel an extension of your body. Maintain a speed of 5 km/h, which prevents stalling and leaves ample reaction time. Remember, steering should be continuous; the worst habit is turning halfway, pausing, and then looking again.