Halt! Observer Pattern in Braking Systems

Halt! Observer Pattern in Braking Systems

In my previous exploration, "Drive and Code - The State Pattern Meets Car Transmissions," we journeyed through the intricacies of car transmissions. We marvelled at the fascinating connection between software design patterns and vehicular systems. Our minds were set in gear (pun intended) to view the world of automobiles through the prism of software design, unravelling the intricate symphony of patterns that underpin both domains. Building upon that momentum, it's time to hit the brakes and dive into another critical component of every vehicle: the braking system.

But why brakes? At its core, a braking system is a masterclass in responsiveness, safety, and control - themes that are also paramount in software design and architecture. Moreover, as cars evolve, so do their braking mechanisms, leading to a plethora of techniques and technologies, much like the myriad patterns and methodologies in software development.

In this article, I aim to merge these two worlds once again. I'll explore the importance of brakes, the diverse types of braking systems (including futuristic regenerative brakes), and the intriguing phenomenon of one-pedal driving in electric vehicles. Furthermore, I will illustrate how the Observer Pattern, a staple in software design, can provide an elegant and robust framework to understand, model, and even potentially innovate within braking systems.

The Significance of Brakes in a Car

When discussing the intricate systems of a car, the braking system often emerges as a paramount feature, synonymous with safety. Its fundamental role is evident; brakes are the primary safety mechanism in any vehicle. Whether navigating bustling city streets or cruising along highways, the ability to decelerate or come to a complete stop can spell the difference between an ordinary drive and a potentially calamitous incident. In the vast tapestry of road scenarios, from sudden traffic changes to unexpected obstacles, brakes are the guardian, ensuring not just the safety of the vehicle's occupants but all road users.

Yet, brakes are not just about safety. They represent control and precision. Beyond merely halting the vehicle, they give drivers the nuanced ability to regulate speed, manoeuvre tight corners, and execute precise tasks like parallel parking. While an engine propels and defines a car's movement, the brakes grant the driver mastery over it.

The brake's adaptability further accentuates this control. A vehicle might traverse rain-soaked roads, snowy terrains, gritty gravel paths, or smooth asphalt, but the demand on the brakes remains consistent. Their ability to offer unwavering performance across varying conditions underlines their versatility and highlights the driver's need to adapt to different environments confidently.

Beyond mechanics and function, brakes are also about feelings: the feelings of trust and confidence they instil in drivers. With the assurance that their vehicle can stop promptly, drivers can focus on the journey ahead, make instant decisions, and genuinely savour the driving experience.

Lastly, in a slightly paradoxical twist, it's worth noting that brakes, in their efficiency, are enablers of speed. While engines might drive a car forward, the reliable assurance of brakes allows for higher velocities. Advanced braking systems, especially those in sports cars and racing vehicles, don't just halt motion; they empower it, underscoring the idea that brakes are truly the enablers of speed.

In encapsulating the essence of braking systems, it's evident that while engines often bask in glory, the brakes, in their quiet diligence, ensure every trip is safe, controlled, and delightful. As we delve deeper into this article, we'll explore how these cornerstone attributes of brakes find parallels in software systems and how the Command Pattern can serve as an illustrative tool for understanding them.

Types of Braking System

Braking systems have continuously evolved within the vast realm of automobiles, each tailored to suit particular needs and vehicle types. While differing in approach, every system harmoniously converges on a singular goal: safely decelerating or halting the vehicle.

The Hydraulic Braking System, common in many of today's vehicles, leverages the non-compressible nature of liquids. This system transmits the force from the brake pedal through brake fluid directly to the brake shoes or pads, creating an efficient force transfer that drivers have come to rely upon.

Yet, looking back, vehicles embraced the simpler Mechanical Braking System. Found in older cars, this direct approach utilized mechanical links, like rods or cables, connecting the brake pedal to the brake shoes. Its straightforwardness and durability made it a mainstay for years.

As we venture into larger vehicles, the Pneumatic Braking System stands out. Designed for the likes of buses and trucks, this system harnesses air pressure. When the brake pedal engages, a buildup of air pressure within the brake lines activates the braking mechanism, showcasing the adaptability of braking technology to different vehicular needs.

Driving into the future, the advent of electric vehicles (EVs) and hybrids brought the innovative Regenerative Braking system to the forefront. Beyond mere braking, this system recaptures the kinetic energy typically lost during the process, converting and storing it back into the vehicle's battery. It's a dance of energy conservation that augments the vehicle's range.

Yet, the world of braking doesn't end there. Some cutting-edge vehicles and trains have adopted the Electromagnetic Braking System. Relying on magnetic fields to generate the braking force, this system offers the distinct advantage of being wear-free, eliminating the conventional friction-based wear and tear.

As the narrative of braking systems unfolds, it's worth noting the changing landscape, especially with the rise of modern electric vehicles and the intriguing concept of "one-pedal driving." Here, lifting off the accelerator can activate regenerative braking, decelerating the vehicle without any need for the traditional brake pedal. It's a novel reimagining of the essence of braking in our electrified age.

These diverse braking mechanisms, while distinct, echo a shared theme: adapting and evolving to the ever-changing demands of vehicles and driving conditions. As we transition into exploring their parallels with software design patterns, especially the Command Pattern, the commonalities between automobiles and software development become increasingly evident.

One-Pedal Driving

Amid the constant innovations in the automotive landscape, the emergence of electric vehicles (EVs) has introduced an intuitive concept: One-Pedal Driving. As futuristic as it sounds, this modern-day driving technique is a vivid representation of technology, efficiency, and adaptability, blending seamlessly.

At its heart, one-pedal driving empowers EV drivers to accelerate, decelerate, and even halt using just the accelerator pedal. This wizardry is made possible predominantly through the aggressive use of regenerative braking. When the accelerator is released, rather than smoothly coasting as with traditional vehicles, the EV actively begins to decelerate. The kinetic energy, which would typically dissipate as heat in conventional braking, is harvested and fed back into the battery, enhancing efficiency and range.

The adaptation curve for drivers entrenched in the traditional two-pedal system might seem steep at first, but many who've transitioned often laud the system's intuitiveness and ease of adaptation. Beyond mere efficiency, one-pedal driving can considerably reduce driver fatigue, especially in relentless stop-and-go traffic scenarios. The less the necessity to juggle between pedals, the more continuous and streamlined the overall driving experience becomes.

Yet, on a personal note, I find myself somewhat ambivalent. As much as I appreciate advancements, there's an undeniable allure in the sensation of coasting, feeling the open road's rhythm, and actively controlling a vehicle's pace. The leap to one-pedal driving feels like a further detachment from those cherished nuances of driving. Having already transitioned from a manual transmission to an automatic, I've felt that bittersweet pang of giving up a layer of tactile connection with my vehicle. While the convenience of an automatic is undeniable, it's a poignant reminder that every technological leap, however beneficial, comes with its own set of trade-offs.

Nevertheless, the importance of safety remains unchanged. With one-pedal driving, unexpected decelerations might catch following drivers unaware. A judicious and gradual adaptation to this system, therefore, is of paramount importance for first-timers.

In the broader perspective, one-pedal driving symbolizes how automotive innovations challenge and redefine our traditional understanding of driving. It transforms the act of driving from a mechanical exercise to an almost seamless, singular experience, much like how software development constantly evolves, pushing boundaries and challenging conventions.

Observer Pattern in Braking

The Observer Pattern is about understanding and reacting to events. An object, termed the "subject", maintains and notifies a list of dependents, the "observers", about any state changes.

In the world of cars, imagine the braking system as the "subject". When you press the brake pedal, this action doesn't singularly decelerate the car. It also illuminates brake lights, adjusts the in-car music volume, or interacts with other integrated systems. All these functionalities, acting as "observers", await the brake event to be signalled. On receiving this signal, they perform their designated actions.

The brilliance lies in the decoupling. The brake system doesn't directly command the brake lights to turn on or the music system to lower its volume. It merely broadcasts its current state, and the linked systems, having "subscribed" to the brake system's notifications, react based on their programming.

In order to capture the intricate dynamics of braking in a car, we start by defining the BrakingState interface. This serves as a snapshot of the braking system's current state, including whether or not the brakes are applied and the intensity of the braking action.

interface BrakingState {
    isBraking: boolean;
    brakingForce: number; // Ranging from 0 (no braking) to 100 (maximum braking force)

Next, we set up the foundation of the Observer pattern. The Observer interface dictates the structure of all observers who wish to be informed about changes in the braking system's state. Meanwhile, the BrakingSystemSubject interface establishes the methods required for managing observer registrations and notifying them of state changes.

interface Observer {
    update(state: BrakingState): void;

interface BrakingSystemSubject {
    registerObserver(o: Observer): void;
    removeObserver(o: Observer): void;
    notifyObservers(): void;

Our primary class, CarBrakingSystem, implements the BrakingSystemSubject interface, becoming the heart of our braking mechanism. This class maintains a list of observers and a current braking state. When brakes are applied or released, the state is updated, and all registered observers are immediately notified. The braking action is also enriched by allowing varying intensities through the applyBrakes function, which accepts a force parameter.

class CarBrakingSystem implements BrakingSystemSubject {
    private observers: Observer[] = [];
    private state: BrakingState = {
        isBraking: false,
        brakingForce: 0

    registerObserver(o: Observer): void {

    removeObserver(o: Observer): void {
        const index = this.observers.indexOf(o);
        if (index > -1) {
            this.observers.splice(index, 1);

    notifyObservers(): void {
        for (let observer of this.observers) {

    applyBrakes(force: number): void {
        this.state = {
            isBraking: true,
            brakingForce: Math.min(100, Math.max(0, force)) // Ensure force is between 0 and 100

    releaseBrakes(): void {
        this.state = {
            isBraking: false,
            brakingForce: 0

In this design, the CarBrakingSystem becomes an observable subject. When a user applies or releases the brakes, the system's state changes, and in response, every observer (like brake lights, anti-lock systems, or even infotainment screens showing real-time data) receives the latest update.

Systems Interacting with the Braking System

Various components and systems in a car are either directly or indirectly affected by the state of the braking system. When you press the brake pedal, not only do the brakes themselves react, but other parts of the car must also respond appropriately. Here, we will discuss a few of these systems and how they can be modelled as observers in our TypeScript code, awaiting notifications from the main braking system.

Brake Lights System

The most apparent system to consider is the brake lights. They illuminate when brakes are applied, signalling to the drivers behind that the vehicle is decelerating.

class BrakeLightsSystem implements Observer {
    update(state: BrakingState): void {
        if (state.isBraking) {
        } else {

    private illuminateBrakeLights(): void {
        console.log('Brake lights are ON');

    private turnOffBrakeLights(): void {
        console.log('Brake lights are OFF');

Anti-lock Braking System (ABS)

The ABS ensures the wheels do not lock up during hard braking, allowing the vehicle to maintain traction. It might adjust the braking force based on the feedback it receives.

class AntiLockBrakingSystem implements Observer {
    update(state: BrakingState): void {
        if (state.isBraking && state.brakingForce > 75) { // Some arbitrary condition for simulation
        } else {

    private activateABS(): void {
        console.log('ABS activated to prevent wheel lock-up.');

    private deactivateABS(): void {
        console.log('ABS deactivated.');

Infotainment System

Modern cars come equipped with infotainment systems that may display real-time vehicle information, including braking status.

class InfotainmentSystem implements Observer {
    update(state: BrakingState): void {
        if (state.isBraking) {
        } else {
            this.showBrakingStatus('No braking applied');

    private showBrakingIntensity(force: number): void {
        console.log(`Braking applied with intensity: ${force}%`);

    private showBrakingStatus(status: string): void {

These are just a few examples of how different systems in a car can interact with the main braking system. In a real-world scenario, there would be more systems interacting in complex ways. But, by adopting the Observer pattern, we can encapsulate and manage these interactions effectively, ensuring each component stays updated with the latest state of the brakes.

The Message Bus Approach

While the Observer pattern, as presented, elegantly models the direct interaction between the braking system and its associated components, it might not be the most suitable approach for complex systems like modern vehicles. In the real world, direct registration of observers could lead to tightly coupled systems where changes to one component might necessitate modifications in others. Here, the concept of a Message Bus (or Event Bus) comes into play.

Message Bus: A Deeper Dive

A Message Bus is a central communication system that allows different parts of a software system (or components of a car's electronic unit) to broadcast or listen to events without being directly connected to each other. In essence, it's like a postal service for software components: they can send messages (events) to the bus or listen for messages without needing to know who specifically sent or will receive them.

The key advantages of the Message Bus over the direct observer registration are:

  1. Decoupling: Components only interact with the message bus, not with each other directly. This reduces the interdependencies and makes the system more modular.
  2. Flexibility: New components can be added, or existing ones can be changed or removed without affecting others. They just need to hook into the message bus.
  3. Scalability: The message bus can handle a large number of events and listeners, making it suitable for complex systems.
  4. Filtering: Components can choose which messages to listen for, allowing for a fine-tuned response system.

Translating to Our Braking System

Let's visualize the braking scenario with a Message Bus:

  1. The braking system, when activated, sends a message to the bus, indicating the braking force and other relevant data.
  2. Systems like the Brake Lights, ABS, and Infotainment, all listen to the bus for braking-related messages. Once a relevant message arrives, they can act on it as necessary.
  3. If we introduce a new component – a Data Logger to record braking patterns – it can simply start listening to the message bus without changing the braking system or other components.
class MessageBus {
    private listeners: { [key: string]: Function[] } = {};

    registerListener(eventType: string, listener: Function): void {
        if (!this.listeners[eventType]) {
            this.listeners[eventType] = [];

    broadcast(eventType: string, data: any): void {
        if (this.listeners[eventType]) {
            for (const listener of this.listeners[eventType]) {

const bus = new MessageBus();

bus.registerListener('braking', (data) => {
    // BrakeLightsSystem logic here

bus.registerListener('braking', (data) => {
    // AntiLockBrakingSystem logic here

// And so on for other systems...

While the Observer pattern has its merits, integrating a Message Bus in scenarios with numerous interacting components offers a more scalable and maintainable approach, especially when these interactions grow in complexity.

User Input to Invoke Braking

While the transition to the Observer pattern with a Message Bus adds a layer of abstraction and decouples our systems, the actual action — braking in this case — still needs to be triggered by a user input. Even with our advanced communication model, the genesis of the brake action remains grounded in the physical world: the driver's interaction with the brake pedal.

Understanding the Interaction

The car's brake pedal serves as the primary interface for the driver to activate the braking mechanism. How hard a driver presses the pedal typically correlates with the urgency or force of the desired braking. Thus, capturing this interaction accurately is crucial.

  1. Pedal Force Detection: Modern vehicles come equipped with sensors that can detect the amount of force applied to the brake pedal. Often measured in units like Newtons, this force can be converted into an electronic signal.
  2. Translating Force to Electronic Message: Once the pedal force is measured and converted into an electronic signal, this information can be dispatched as a message to the Message Bus.
  3. Message Dissemination: The Message Bus then broadcasts this information to all relevant systems. Upon receiving this message, our braking system would initiate the braking process proportionate to the detected force. Other systems, like Brake Lights or ABS, would act accordingly based on the data.

Sample Implementation

In our software analogy, this can be modelled as:

class BrakePedal {
    private bus: MessageBus;

    constructor(bus: MessageBus) {
        this.bus = bus;

    press(force: number): void {
        // Here, the force can be a value between 0 (no pressure) to 100 (maximum pressure)
        // Convert this force into a suitable message format
        const brakeData = {
            type: 'braking',
            force: force
        // Broadcast the brake message to the bus
        this.bus.broadcast('braking', brakeData);

const carBrakePedal = new BrakePedal(bus);

The driver's intent to brake, gauged by the force applied on the pedal, is thus translated into a digital message and disseminated across the car's systems using the Message Bus. The granularity of the force measurement can also help in nuanced brake operations, like gentle slowing down versus an emergency stop.

While the Observer pattern with the Message Bus has changed how the components of our system communicate, the fundamental interaction — the driver pressing the brake pedal — remains unchanged. It's a testament to the versatile nature of software design patterns that they can accommodate and abstract various layers of complexity without altering the core user experience.

Error Handling

One of the most crucial aspects of any system, especially one as critical as a vehicle's braking system, is error handling. Given the safety-critical nature of this function, having robust and reliable error-handling mechanisms in place is non-negotiable.

Identifying Potential Errors

There are multiple points in the braking process where errors could occur:

  1. Sensor Malfunction: The sensors measuring the pedal force could malfunction, either not detecting the force correctly or not detecting it at all.
  2. Message Broadcast Failure: An error might occur while broadcasting the brake message to the Message Bus, leading to no braking action despite the user's input.
  3. Braking System Malfunction: The braking system itself might face a mechanical or electronic issue, rendering it unresponsive to the brake messages.

Handling Errors Gracefully

Given these potential error points, our software design should:

  1. Monitor Sensors Constantly: Continuously check the health and response of the sensors to ensure they are working correctly.
  2. Acknowledge Message Receipt: Systems should send back an acknowledgement whenever a message is broadcasted to the Message Bus. This way, we can be certain that the message was received and acted upon.
  3. Fallback Mechanism: If the primary braking system fails, there should be a fallback or secondary mechanism to ensure the vehicle can still decelerate or stop.
  4. Error Broadcast: In the event of an error, the problematic system should broadcast an error message to the Message Bus, notifying other systems of the issue. For example, the dashboard might light up a warning sign or trigger an audible alert.

User Notification

When it comes to letting the driver know of a potential problem:

Visual Alerts

These can include warning lights on the dashboard, such as the brake system warning light, which illuminates if there's a problem with the braking system.
Audible Alerts

Sounds or chimes can alert the driver to a problem, especially if it's something that requires immediate attention.
Tactile Feedback

Some modern vehicles can provide tactile feedback, like pedal pulsation, to indicate specific issues, such as ABS activation.

We can employ error codes to ensure that our braking system communicates errors consistently and efficiently. These codes allow us to rapidly identify and handle specific issues, which is particularly vital in a car's integrated systems.

Defining Centralized Error Codes and Messages

By defining a set of error codes and their corresponding messages, we ensure that the entire system references a single source of truth:

enum BrakeSystemErrorCodes {
    // ... additional error codes ...

const BrakeSystemErrorMessages = {
    [BrakeSystemErrorCodes.SENSOR_MALFUNCTION]: 'Brake pedal force sensor malfunction.',
    [BrakeSystemErrorCodes.MESSAGE_BROADCAST_FAILURE]: 'Failed to broadcast a system message.',
    [BrakeSystemErrorCodes.BRAKING_SYSTEM_MALFUNCTION]: 'Braking system malfunction detected.',
    // ... additional error messages ...

Broadcasting Errors with Codes

The braking system will broadcast errors using these centralized codes:

class BrakeSystemObserver implements Observer {
    // ... previous methods ...

    onError(errorType: string): void {
        let errorCode: BrakeSystemErrorCodes;
        switch(errorType) {
            case 'sensorMalfunction':
                errorCode = BrakeSystemErrorCodes.SENSOR_MALFUNCTION;
            case 'systemMalfunction':
                errorCode = BrakeSystemErrorCodes.BRAKING_SYSTEM_MALFUNCTION;
            // ... other error cases ...

        const errorMessage = BrakeSystemErrorMessages[errorCode];
        this.bus.broadcast('error', { code: errorCode, message: errorMessage });

Mapping Error Codes to Dashboard Warning Lights

To allow the dashboard to respond to errors appropriately, we can map error codes to specific warning lights:

const DashboardWarningLights = {
    [BrakeSystemErrorCodes.SENSOR_MALFUNCTION]: 'sensorErrorLight',
    [BrakeSystemErrorCodes.BRAKING_SYSTEM_MALFUNCTION]: 'brakeSystemErrorLight',
    // ... mappings for other error codes ...

class DashboardDisplay {
    private bus: MessageBus;
    constructor(bus: MessageBus) {
        this.bus = bus;

    displayError(error: { code: BrakeSystemErrorCodes, message: string }): void {
        const warningLight = DashboardWarningLights[error.code];
        // Logic to display the detailed error message, if required

    activateWarningLight(lightName: string): void {
        // Logic to light up the specific warning indicator on the dashboard

const brakeSystemObserver = new BrakeSystemObserver(bus);
const dashboardDisplay = new DashboardDisplay(bus);

bus.register('error', dashboardDisplay.displayError);

The system becomes more maintainable and streamlined by centralizing error codes, messages, and their corresponding dashboard warning lights. It reduces the likelihood of inconsistencies and simplifies future updates to the error-handling mechanism.

Bringing the Vehicle to a Safe Stop

When faced with critical failures, especially in systems as fundamental as brakes, the vehicle must have measures in place to mitigate the potential dangers. One such measure is an emergency stop protocol, which is activated automatically if the main braking system fails. This protocol can involve multiple methods of decelerating the car while alerting the driver and nearby vehicles about the ongoing emergency.

Engaging Emergency Braking Systems

An emergency braking system can be a secondary, fail-safe braking mechanism, different from the main system. It's activated only in emergencies and works independently of the primary system to ensure there's no common point of failure.

class EmergencyBrakeSystem {
    engageEmergencyBrakes(): void {
        // Logic to engage emergency brakes
        console.log("Emergency brakes activated!");

Once the main brake system identifies a malfunction, it can signal the emergency system to activate:

class BrakeSystemObserver implements Observer {
    // ... previous methods ...

    onError(errorType: string): void {
        // ... existing error handling ...

        if(errorType === 'systemMalfunction') {
            this.isOperational = false;

const emergencyBrakeSystem = new EmergencyBrakeSystem();

Alerting Surroundings

In tandem with the emergency brakes, the vehicle should also warn its surroundings, be it other vehicles or pedestrians. Flashing hazard lights, honking in a specific pattern, or even sending out emergency signals in vehicles equipped with vehicle-to-vehicle communication can serve this purpose.

class VehicleAlertSystem {
    emitEmergencySignals(): void {
        // Activate hazard lights, horn, etc.
        console.log("Emergency signals activated!");

const vehicleAlertSystem = new VehicleAlertSystem();

bus.register('error', (error: { code: BrakeSystemErrorCodes, message: string }) => {
    if (error.code === BrakeSystemErrorCodes.BRAKING_SYSTEM_MALFUNCTION) {

Incorporating such measures ensures that, in the event of a malfunction, the vehicle prioritises stopping safely and communicates the danger to its surroundings, minimizing potential hazards. It embodies the ethos that the best systems are reactive and proactive, anticipating possible dangers and having robust protocols in place.


As we journeyed through the intricate workings of a car's braking system, it's evident that the vehicles we often take for granted are marvels of both engineering and software design. Just as intricate mechanical systems ensure our safety on the road, adept software design patterns offer robustness and flexibility in our software applications.

We explored the Observer pattern and how it lends itself naturally to situations where multiple components need to react to a change or an event, much like various parts of a car responding to braking actions. Through TypeScript examples, we saw how the braking system can emit events, which are then captured and acted upon by various observers – be it brake lights, dashboards, or emergency systems.

Furthermore, as personal preferences evolve and technology advances, the Observer pattern's flexibility shines, allowing for seamless integration of various braking technologies, from traditional hydraulic systems to the innovative regenerative brakes.

For many of us, the joy of driving goes beyond just getting from point A to B. It's about the experience, the connection between the driver and the machine. By understanding the deeper interactions within, we not only appreciate these marvels but also become better equipped to design software systems that mirror their efficiency, adaptability, and resilience.

Drawing parallels between automotive systems and software design makes abstract concepts more tangible and reminds us of the interdisciplinary nature of problem-solving. As technology continues to advance, the lines between different domains blur, fostering a playground of innovation. As developers and enthusiasts, it's exciting to be at this intersection, harnessing patterns and principles to drive the future.