What types of braking systems are used in trains?

The correct answer encompasses the main types of braking systems utilized in trains: air brakes, dynamic brakes, and hand brakes.

Air brakes are the primary braking system used in most freight and passenger trains. They function by utilizing compressed air to activate brake cylinders on each car, which then apply force to the wheel brakes. This system is efficient for controlling the speed of heavy trains over long distances.

Dynamic brakes are another critical component, especially in electrical and diesel-electric locomotives. They work by converting the train’s kinetic energy into electrical energy that can be dissipated as heat through resistors. This system is beneficial for slowing down trains without the need for constant friction from traditional brakes and helps to reduce wear on brake components.

Hand brakes are manually operated and serve as a backup or supplementary system, typically used when trains are stationary to prevent movement. Crew members operate these brakes to secure trains on inclines or during loading and unloading activities.

Together, these braking systems provide a comprehensive approach to train safety and control, ensuring effective stopping power under various conditions. The other options do not include all three types of breaking systems, which makes the chosen answer comprehensive and accurate.