What does looking at the ground beside a moving vehicle help you assess?

Looking at the ground beside a moving vehicle helps you assess the speed of the vehicle. When you observe the ground or roadway surface passing beneath the vehicle, you can gauge how quickly it is moving based on how fast the ground is moving relative to your point of view. This technique allows drivers to make quicker decisions regarding their own speed and trajectory, helping them maintain safe distances and avoid potential hazards.

While assessing other factors such as direction, vehicle size, or weather conditions is essential for safe driving, these aspects are typically determined through different observations. For instance, direction can be inferred from the vehicle's position and movement in relation to surroundings, size can be estimated by visual comparison, and weather conditions require specific awareness of environmental factors. Therefore, focusing on the ground is particularly effective for estimating speed.