A recent Bosch test drive of over 2000 miles in a mix of climatic conditions on public roads has paved the way for the market launch of a brake-by-wire system this autumn.

Orders are already in place from various vehicle makers and Bosch expects 5.5 million vehicles globally to be equipped with brake-by-wire by 2030.

Drive-by-wire is a seemingly exotic concept whose essence is to remove the driver from direct mechanical or hydraulic contact with the car’s steering or brakes.

Instead, the driver’s inputs through the steering or brake pedal send an electronic signal to a computer, which activates the brakes or steering through actuators instead.

A full brake-by-wire system would not only decouple the driver from the brakes but also switch to a ‘dry’ system, with hydraulics replaced by electromechanical brake calipers.

Although the Bosch system mechanically decouples the driver from the system, sending an electronic signal instead, the brake calipers are still applied hydraulically.

In a conventional braking system, the brake pedal acts directly on a master hydraulic cylinder, usually mounted ahead of the driver on the firewall in the engine bay.

But Bosch’s set-up removes the need to mount any braking system components on the firewall. Instead, they can be mounted where it best suits NVH (noise, vibration and harshness), crash safety and ease of manufacturing.

The brake pedal sends a signal to hydraulic brake-by-wire and ESP actuators that work independently of one another and can both build up hydraulic pressure to apply the brakes on all four wheels.

Each is connected to its own electrical channel, so if anything goes wrong with one, the other can still do the job. This feature, called ‘redundancy’, is something all such electronic safety-related systems have.

Perfecting reliable brake-by-wire systems is becoming more pressing as the use of automated driving features ramps up and with the possibility of fully autonomous cars on the horizon.

Continental introduced a similar technology, the MK C1, in 2016, which was adopted by Alfa Romeo for the Giulia and Stelvio in 2018. In 2022, it evolved into the MK C2 and is described as a ‘one-box solution’ because it integrates the master cylinder, brake booster and control systems (ABS and ESC) into a single, compact unit.

The brake pedal is decoupled from the hydraulics and actuates a pressure pedal-feel simulator to “provide the driver with a familiar braking experience”.

Continental says one advantage to the driver is no change in pedal feel during regenerative braking on an EV, or when blending recuperative braking with the conventional friction brakes.

Brake-by-wire systems should help with energy efficiency too. Continental says its system leaves no residual pressure in the brake calipers after braking, translating to a reduction of 5g/km of CO2 in WLTP testing.