Understanding the Mechanics of Brake Override Systems

Brake systems were once straightforward. Depressing the pedal activated a mechanical mechanism that applied brake shoes directly to the wheels. Although brake pads still rely on friction to halt your vehicle, technological innovations such as ABS, brake assist, and now brake override systems have transformed the process from pedal press to vehicle stop. The direct link between your foot and the brake pad has been replaced by advanced electronics.

Brake override is also referred to as a smart pedal. These systems utilize sensors to detect simultaneous pressing of the gas and brake pedals. They identify this as an unusual driving behavior, indicating a potential issue. The vehicle's central computer then employs various methods to safely decelerate the car.

This technology debuted in the BMW 750 during the late 1980s as a performance upgrade for heel-and-toe racing techniques, where a driver uses one foot to operate two pedals simultaneously. Since 2001, every BMW model has incorporated brake override. Chrysler adopted the technology in its 2003 models. Today, numerous car manufacturers utilize this system, with more expected to follow [source: Motavalli].

When it comes to technology, let’s explore the components and functionality of a brake override system on the following page.

Brake Override System Technology

The innovation behind brake override systems stems from the same technology enabling numerous safety features: a fully integrated electronic system. Once BMW developed its electronic throttle, or 'drive-by-wire' system, which replaced mechanical or hydraulic controls with electronics, incorporating a brake override system became straightforward. The necessary wiring and computer infrastructure were already in place.

As Nick Cappa, Chrysler’s engineering and technology spokesperson, explained, 'Electronic controls allowed automakers to manage multiple systems through a single action.' This means, theoretically, an automaker could link the dome light to the radio, as both are connected via sensors communicating with the computer. More importantly, the system can detect issues with the brake and gas pedals and safely reduce the car’s speed.

For brake override systems to function, they need sensors on the brake and gas pedals, a computer to determine the appropriate action, and wiring to connect everything. If the system identifies an issue, such as the driver pressing the brake while the car accelerates, the computer can activate the brake override and 'derate' the engine—automotive jargon for reducing power. It can achieve this in several ways:

The car’s response depends on the manufacturer’s programming for scenarios where both the gas and brake pedals are engaged. Regardless of the method, the objective remains consistent—bringing the car to a safe stop.

Toyota, for instance, employs accelerator pedal sensors, brake light switch circuits, and vehicle speed sensors to identify potential loss of control. If the car is moving at 5 mph (8 kph) or faster and the brake pedal is held for over half a second, the system shifts the engine to idle to reduce speed. The half-second buffer prevents the system from interfering during hill starts or when the driver is maneuvering for traction in snow or mud.

While these features are impressive, what advantages do brake override systems offer? Continue reading to discover more.

Benefits of Brake Override Systems

When a car accelerates unexpectedly, most drivers instinctively press the brake pedal. This natural reaction has inspired the development of brake override systems. The primary advantage of these systems is enhanced safety. Whether the issue stems from human error or a technical malfunction, the system serves as a safeguard, reducing the risk of high-speed collisions.

According to Nick Cappa at Chrysler, the computer assesses the driver’s intentions and compares them to the actual actions. If sensors detect a mismatch, such as the car accelerating while the driver is braking, the computer activates the brake override to slow the vehicle. With the growing reliance on electronic throttles to control speed, having an electronic system to address throttle-related issues is a significant advantage.

The importance of brake override systems becomes evident when examining vehicles without them. For instance, Toyota’s October 2009 recall, prompted by reports of unintended acceleration, highlights this issue. By early 2010, the National Highway Traffic Safety Administration had recorded 43 complaints of fatal Toyota-related accidents since 2000, resulting in 52 deaths and 38 injuries. Lawmakers argued that these tragedies might have been prevented with brake override systems, as reported by the New York Times.

Given their potential to save lives, lawmakers are exploring ways to regulate brake override systems effectively. Continue reading to learn which vehicles currently utilize this technology.

Do All New Cars Have Brake Override Systems?

By early 2010, many new vehicles featured brake override systems, though they were not yet standard. The Obama administration encouraged, but did not mandate, that automakers incorporate this system in new cars following Toyota’s large-scale recall due to acceleration problems.

Automakers such as BMW, Chrysler, Audi, Mercedes-Benz, and Volkswagen have adopted brake override systems in many of their models. Chrysler, for example, includes the system in 97% of its vehicles, excluding only the PT Cruiser. Hyundai planned to equip all new models with the system by March 2010, while Toyota, Lexus, and Scion aimed to do so by the end of 2010 [source: Motavalli, U.S. News].

As vehicles increasingly rely on integrated electronic systems, such as drive-by-wire technology, rather than mechanical accelerators, advanced safety features like brake override are becoming more common. However, this system cannot address situations where drivers mistakenly press the gas instead of the brake. Some issues remain beyond the reach of technology.