A brake run on a roller coaster is any section of track that utilizes some form of brakes to slow or stop a roller coaster train. There are various types of braking methods employed on roller coasters, including friction brakes, skid brakes, and magnetic brakes. The most common is a fin brake, an alternative name for a friction brake, which involves a series of hydraulic-powered clamps that close and squeeze metal fins that are attached to the underside of a coaster train. Roller coasters may incorporate multiple brake runs throughout the coaster's track layout to adjust the train's speed at any given time.

The different types of brake runs are classified under two main categories: trim brakes and block brakes. A trim brake refers to a braking section that slows a train, while a block brake has the ability to stop a train completely in addition to slowing it down. Block brakes are important to roller coasters that operate more than one train simultaneously, in the event that one train stalls on a portion of the track. While modern roller coasters have at least one computer-controlled brake run embedded in the track, older coasters such as The Great Scenic Railway at Luna Park Melbourne may have brakes onboard the train and rely on a brakeman operator to apply them as needed.

Trim brakes are brake run sections that reduce the speed of the train but are not intended to stop the train completely.^[1] They may be engineered into a ride during design in anticipation of certain trouble spots, or later retrofitted in areas where trains are traveling at higher-than-expected speeds. Trim brakes can also be added for safety reasons, lowering the g-force riders experience at various points throughout the track layout, or for preventative maintenance reasons, reducing wear-and-tear on the trains or track. A proximity sensor often precedes the trim brake in order to identify the current speed of the passing train and determining how much the brake will need to slow the train, if at all.^{[citation needed]}

Block brakes also have the ability to slow the train but serve the additional purpose of being able to stop the train completely.^[1] This is required on roller coasters that operate more than one train simultaneously on the track. They act as virtual barriers between the trains running on the roller coaster, preventing collisions should one train stop along the course for any reason. Block brake sections must also be engineered so that the train can begin moving again upon release, either by using a slight downward slope to let gravity take its course or by using drive tires to push the train out of the block. These are commonly called mid-course brake runs.

Roller coasters utilize a variety of braking methods that have evolved over time.

Skid brakes involve a long piece of material, often ceramic-covered, that is situated in the middle of the track parallel to the rails. When the brake is engaged, the skid raises and causes friction against the underside of the train, reducing its speed. They can be used to slow or stop the train. Skid brakes were one of the first advancements in roller coaster braking and are typically found on older wooden coasters, such as Leap the Dips, the world's oldest roller coaster still in operation.

Friction brakes, commonly called fin brakes, involve a computer-controlled clamping system that squeeze metal fins attached underneath the train.^[1] Friction brakes can be used to slow or stop the train and are the most common form of brakes found on modern roller coasters.^[1] They can involve thick metal box beams or thin metal plates. They slide between pairs of friction pads similar to automotive brake pads.

Friction brakes are designed to be fail-safe, allowing them to engage even when there is a loss of power. They are also constructed with a certain measure of redundancy, incorporating extra sets of brakes in the event that one set fails. Opening is done by a bellows type of air-operated actuator, with each set of brakes fitted with its own air supply system that is controlled by supply valves that open and release the brake when it is safe to do so. A heavy spring usually made of steel is used to hold the brake closed when engaged.

Instead of relying on friction, which can often be affected by weather conditions such as rain, magnetic brakes apply resistance through magnetism without making direct contact with the train. They are made up of one or two rows of neodymium magnets. When a metal fin made of copper or a copper-aluminum alloy passes between the rows of magnets, eddy currents are generated in the fin, creating a magnetic force that opposes the fin's motion. The resultant braking force is directly proportional to the speed at which the fin is moving through the brake element.

Magnetic brakes can be found in two configurations:

• The brake elements are mounted to the track or alongside the track and the fins are mounted to the underside or sides of the train. This configuration looks similar to friction brakes.
• The fins are mounted to the track and the brake elements are mounted to the underside of the train. This configuration can be found on Intamin Accelerator Coasters.

Magnetic brakes are silent and provide a smoother riding experience than friction brakes, gradually increasing the braking power so that the people on the ride do not experience rapid changes in deceleration. Intamin began incorporating them with their Accelerator Coaster models, as well as Bolliger & Mabillard beginning in 2004 with their installation of Silver Bullet, the first inverted coaster to feature magnetic brakes. There are also third-party companies, such as Magnetar Technologies Corp., which provide a service to retrofit existing coasters with magnetic braking technology to increase safety, improve rider comfort, and lower maintenance costs and labor.^{[citation needed]}

A disadvantage of magnetic braking is that the eddy force is not usually stable enough to hold a train completely still, and as such cannot be used as block brakes. Magnetic brakes are often complemented by an additional set of friction brakes or "kicker wheels", rubber tires that make contact with the train and effectively park it. Another disadvantage is that they cannot be conventionally disengaged like other types of brakes. Instead, the fins or magnets must be retracted so that the fins no longer pass between the magnets. Accelerator Coasters, for example, have a series of magnetic brake fins located on the launch track. Prior to the train's launch, the brakes are retracted out of the way to allow the train to reach its maximum speed. After launch, the brake fins are raised back in position to stop the train in the event of a rollback. An example of this can be found on Kingda Ka at Six Flags Great Adventure.

While skid brakes already existed by the time Scenic Railway had been conceived, LaMarcus Adna Thompson decided against using these brakes for his Scenic Railway roller coasters, and instead opted for using a brakeman system in a similar to manner to those used on gravity trains. The brakeman would sit in the center of the train and pull a lever to apply a brake and slow down the train. Over thirty Scenic Railways were constructed, but only a small number remain in operation.

• List of roller coaster elements