What is a common consequence of harsh braking in a combination-unit vehicle?

Harsh braking in a combination-unit vehicle can lead to a risk of jack-knifing or skidding due to the dynamics involved with such vehicles. When a driver applies the brakes suddenly, it can cause the rear trailer to brake more effectively than the front tractor. This imbalance can lead to the trailer pushing the tractor out of alignment, increasing the chance of the trailer swinging out, which is known as jack-knifing.

Additionally, harsh braking can result in the wheels locking up, especially if the vehicle is not equipped with anti-lock braking systems (ABS), leading to a loss of traction and control. When the tires lose grip on the road, skidding can occur, making it difficult to control the vehicle's direction. This is particularly hazardous for combination-unit vehicles, which are generally longer and require more effort to maneuver safely compared to standard passenger vehicles.

In contrast, improved handling, enhanced braking efficiency, and a guarantee of road safety are unrealistic outcomes of harsh braking conditions, as these would imply a level of control that is compromised during sudden deceleration in complex vehicle configurations.