Why throttle and brake should not be used simultaneously

Modern cars are equipped with advanced safety features which include the prioritization of brakes when both brakes and throttle are applied at thesame time.
Last modified
11 Feb, 2024

Throttle is a valve that regulates the supply of air or fuel for efficient combustion in a vehicle's engine.

The driver is able to control the throttle through the throttle pedal by using his or her foot.


Brakes are used the slow or stop the motion of the wheels of a vehicle.

The driver controls the brakes by applying pressure to the brake pedal using the foot.

Brake and accelerator pedal

Modern cars have a lot of safety and convenience features incorporated into them. One of the safety features is prevention of unintended acceleration.


What is unintended acceleration?

This is a situation where the driver does not intend to accelerate the vehicle but the acceleration happens. There are majorly two ways unintended acceleration happen.


Ways unintended acceleration happen

1. System error

This mostly happens due to errors in the systems of the vehicle. For instance, the ECU commanding the drive-by-wire throttle system to accelerate when it should not.

2. Driver's error

This mostly happens when the driver intends to press the brake pedal but presses the throttle pedal instead or presses both pedal instead of the brake pedal only.


Safety feature to prevent unintended acceleration

In the case of the last scenario where the driver may mistakenly press both brake and throttle pedals, there is a safety feature which gives the brake priority over the throttle. This causes the throttle system to disengage while the brake work.

In some cases, this throws the throttle system into limp mode and the driver begins to experience no throttle response until the system is reset.


This is one major reason why it is not right to place foot on both accelerator and throttle pedals. This can cause malfunctioning of the throttle system. Often times, it is misdiagnosed resulting in unwarranted change of parts and cause wastage of money.