Why Do Buses Always Stop With a Jerking Movement?

Introduction

Have you ever been on a bus that suddenly jerks to a stop, leaving you and your belongings in disarray? In contrast, cars often manage to come to a smoother halt. This difference is due to a variety of factors including weight, braking systems, driver techniques, and suspension systems. Let's explore these factors in detail and understand why buses can't always stop with the same ease as cars.

The Secret of Smooth Stopping in Cars

Car drivers can achieve butter-smooth stops with great skill, often acquired through years of experience. A key technique is a minuscule easing of the brakes at the very last moment, allowing the car's residual traction to absorb the remaining momentum. This requires both precision and a bit of luck. I, with over 60 years of driving experience, can attest to the mastery needed but I'm far from perfect—experience is indeed everything.

When stopping on uphill terrain, a seasoned driver may even avoid using the brakes altogether, relying on gravity and maintained momentum to slow the car. However, such techniques require a high level of expertise and can be challenging for newer drivers. A smooth stop is rarely achieved on the first attempt, but with practice, most people can master this skill within a few minutes of driving practice.

Why Buses Experience Jerking Stops

When it comes to buses, the jerking motion during stops is often due to several specific factors:

Weight and Size

Buses are significantly heavier than cars. This increased mass necessitates more time and distance to come to a complete stop. When a bus driver applies the brakes, the inertia of the bus can cause it to lurch forward, followed by a sudden deceleration. This scenario is more pronounced than the smooth slowing down experienced in cars.

Braking System

Most buses are equipped with air brakes, which operate differently from the hydraulic brakes commonly found in cars. Air brakes rely on compressing air to create braking force, which can lead to a delayed response. This delay can result in a more abrupt stop, which contrasts sharply with the smoother, quicker response of hydraulic brakes. Consequently, the stop may feel more jarring and less controlled.

Driver Technique

Bus drivers often face the challenge of stopping quickly and frequently, especially in urban environments where they need to pick up and drop off passengers. This frequent stopping in close proximity can lead to a more abrupt application of the brakes, contributing to the jerking motion. Experienced car drivers, on the other hand, may have more flexibility to apply the brakes more gently, allowing for smoother deceleration.

Suspension System

The suspension systems of buses are designed for stability and heavy loads, which can result in a stiffer ride. This stiffness can make it more difficult for the bus to absorb the stopping forces as effectively as a car with a more flexible suspension. The result is a less smooth ride and a more noticeable jerking motion when braking.

Load Variability

Buses frequently carry a varying number of passengers, which can affect their center of gravity and weight distribution. This variability is one of the reasons why stopping a bus can be more challenging. Differences in the way passengers are seated or the weight of luggage can impact the bus's ability to stop smoothly.

Conclusion

In summary, the jerking motion when a bus stops is a result of its larger size, air braking system, driver technique, stiffer suspension, and load variability. While it's understandable that this can be uncomfortable, it's often a natural consequence of the bus's design and operational requirements. Drivers work under pressure and the frequent stops add to the challenge. However, if a bus always jerks to a stop, it may indicate that the driver is not as skilled or experienced as they should be. With regular training and experience, bus drivers can improve the smoothness of their stops, making for a more comfortable ride for everyone involved.