Components Are Not Enough – Drive-by-Wire as a Complete System

From Modular Kits to System Responsibility

In discussions about Drive-by-Wire, it is often implicitly assumed that a fully functional overall system can be assembled from high-quality individual components. Steer-by-Wire, Brake-by-Wire, redundant control units — all of these already exist. The conclusion seems obvious: if each component is safe on its own, the overall system must be safe as well.

This assumption is technically understandable — but it falls short.

Safety, availability, and controllability in autonomous vehicles do not emerge from the sum of components. They emerge from system behavior. And system behavior cannot be calculated modularly.

Why Safety Is Not Additive

In traditional vehicle architectures, it was long acceptable to assess safety at the component level. The driver acted as the higher-level authority, capable of intervening if necessary. Accordingly, many systems were designed to transition into a safe state in the event of failure — for example, by shutting down or reverting to mechanical fallback functions.

Autonomous systems fundamentally change this logic.

When no driver is present, the system itself becomes the final decision-maker. In this context, safety is no longer the result of individually secured functions. It is the outcome of coordinated interaction among all subsystems — including their transitions, dependencies, and failure modes.

A Brake-by-Wire module may be ASIL-D compliant on its own.
A Steer-by-Wire system may be as well.

But what happens when both must operate simultaneously under degraded conditions?
How do they behave if communication pathways are compromised?
Which priorities apply in a boundary situation?

These questions cannot be answered at the component level. They must be decided and assumed at the system level.

The Integration Gap in Practice

This is precisely where a structural gap in the market becomes visible.

Many customers — particularly OEMs, system integrators, or operators of autonomous fleets — receive individual Drive-by-Wire building blocks from major suppliers. These building blocks are technically mature, high-performing, and certified.

What they do not provide is a binding statement about the behavior of the complete system.

The consequence:

Responsibility for integration, safety argumentation, and fail-operational strategies shifts to the customer. The customer must determine how components are combined, how redundancies interact, and how the vehicle continues to operate in the event of failure.

This is not a trivial task.
It is a safety-critical system responsibility.
It is a safety-critical system responsibility.

Drive-by-Wire as an Architectural Question

A true Drive-by-Wire system does not begin with selecting individual components. It begins with architecture.

That architecture includes, among other elements:

• a clear separation and redundancy of safety-critical functions
• deterministic communication pathways
• harmonized control and monitoring mechanisms
• consistent energy management
• and a system-wide safety concept that not only detects faults but manages them

The decisive factor is not merely that redundancy exists — but how it is utilized. Redundancy without system logic leads, at best, to standstill. At worst, it results in unpredictable behavior.

System thinking means bringing these aspects together from the outset — not only during integration.

Platform Independence as a System Criterion

Another indicator of systemic maturity is platform independence.

Many Drive-by-Wire solutions are deeply embedded in specific vehicle platforms. This simplifies series production but limits transferability to other vehicle types or deployment in existing fleets.

Autonomous applications, however, rarely arise exclusively in new vehicles. They emerge where vehicles are already in operation and are to be automated. For this reality, a Drive-by-Wire system is required that can adapt to different platforms without having to reinvent its safety logic.

This, too, is not a characteristic of individual components, but the result of a systemic architectural decision.

Why True System Providers Are Rare

System responsibility means more than delivery.

It means making statements about the overall vehicle behavior — technically, regulatorily, and operationally.

That is demanding.

It requires experience across product generations, deep understanding of safety-critical systems, and the willingness to assume responsibility rather than transferring it across interfaces. A true drive-by-wire system provider does not merely deliver actuators and control units.

They define how the vehicle behaves under all conditions — including degraded modes.

For this reason, there are only a few providers worldwide who treat Drive-by-Wire not as a collection of functions, but as a coherent, integrated system — and implement it accordingly.

A Necessary Shift in Perspective

The question operators of autonomous systems should ask is therefore not: Which components are available?

But rather: Who assumes responsibility for the system?

As long as Drive-by-Wire is primarily understood as a modular kit, autonomous driving remains an integration project. Only when vehicle control is conceived as a complete system does the foundation for scalable, safe operation emerge.