When Autonomous Vehicles and Bicycles Collide: Legal Challenges in Proving Fault

As autonomous vehicles continue to expand across California roadways, a new category of bicycle accident claims is emerging: collisions between cyclists and self-driving cars. While these vehicles are designed to reduce human error, they introduce new and often complex questions about how to prove fault when something goes wrong.

For injured cyclists, these cases are rarely straightforward. Unlike traditional accidents involving a human driver, liability may hinge on how a vehicle’s sensors, software, and decision-making systems function in real time. Understanding the legal and evidentiary challenges in these cases is critical to building a strong claim. At Kalfayan Merjanian, LLP, our California bicycle accident attorneys represent injured cyclists and analyze these collisions through both traditional negligence principles and modern product liability law.

Why Fault Is More Difficult to Prove in Autonomous Vehicle Cases

In a typical bicycle accident, proving fault often comes down to whether a driver violated a traffic law, such as failing to yield, making an unsafe turn, or driving while distracted. Evidence like witness statements, traffic citations, and physical damage can help establish liability.

In autonomous vehicle cases, however, the focus shifts. The key issue is often not just what happened, but why the vehicle made the decision it did. The “driver” may not have been actively controlling the vehicle, and critical decisions may have been made by software rather than a human. In some cases, the cause of the crash involves a system failure rather than a clear traffic violation.

As a result, proving fault requires a deeper, more technical investigation than in a standard accident case.

The Role of Human Oversight

Many vehicles on California roads are not fully autonomous. They operate with advanced driver-assistance systems that still require human monitoring. In these situations, a human driver may still be legally responsible if they fail to remain attentive or ignore warnings to take control. Determining whether the human operator or the system was in control at the time of the collision is often a central issue. If the driver failed to intervene when they reasonably should have, liability may still be based on traditional negligence principles.

When the Technology Is the Problem

In other cases, the evidence may point to a failure of the autonomous system itself. These failures can include:

• Failure to detect a cyclist in a bike lane or roadway
• Misjudging the speed or distance of an approaching bicycle
• Inadequate response time to avoid a collision
• Unsafe turning or lane-change decisions

When these types of failures occur, the case often shifts toward product liability, where the focus is on whether the vehicle or its systems were defective or unreasonably dangerous.

Product Liability in Bicycle Collision Cases

Product liability law allows injured victims to hold companies responsible when a product does not perform safely. In the context of autonomous vehicles, this can involve issues with sensors, software, or overall system design. Claims may be based on a design defect, meaning the system is inherently unsafe under certain conditions, or a failure to warn, where users are not adequately informed about the system’s limitations. For example, if a vehicle’s system cannot reliably detect cyclists in certain environments but is still used in those conditions, that limitation may become a central issue in the case. Unlike negligence claims, product liability does not require proof that the company acted carelessly. The focus is on whether the system itself was unsafe.

The Importance of Digital and Technical Evidence

One of the most significant challenges in these cases is accessing and interpreting the data generated by the vehicle. Autonomous systems continuously record information about their surroundings and internal decision-making processes.

Key evidence may include:

• Event data recorder (black box) information
• Sensor and camera recordings
• Software logs showing how the system interpreted the cyclist
• Speed, braking, and steering inputs
• Internal system alerts or warnings

This data can reveal whether the vehicle detected the cyclist, how it classified them, and what actions it took in response. Because much of this information is controlled by manufacturers or fleet operators, early legal action is often necessary to preserve it.

Competing Narratives and Defense Strategies

Autonomous vehicle cases often involve multiple defendants, each attempting to shift responsibility. It is common for parties to dispute whether the cyclist, the human operator, or the vehicle system was at fault. For example, defense arguments may claim that the cyclist was riding unpredictably or entered the roadway suddenly, or that the human operator failed to intervene in time. In other cases, companies may argue that the system functioned as designed and was not defective. These competing narratives make it essential to build a case supported by detailed evidence and expert analysis.

The Role of Experts in Proving Fault

Because of the technical nature of these cases, expert testimony is often essential. Accident reconstruction specialists, engineers, and software experts may be needed to explain how the collision occurred and whether the system performed as expected. Experts can analyze vehicle data, reconstruct the sequence of events, and evaluate whether the autonomous system met safety standards. Their role is often critical in helping a jury understand complex technical issues.

Comparative Fault and Blame-Shifting

California follows a comparative fault system, which means that more than one party can share responsibility for an accident. In bicycle cases, insurance companies often attempt to shift blame onto the cyclist. They may argue that the cyclist failed to follow traffic laws, was riding outside a bike lane, or was not visible. However, these arguments must be evaluated in context. Even if a cyclist is partially at fault, they may still recover compensation. The key question is whether the autonomous vehicle and any responsible parties acted reasonably under the circumstances.

Injuries and Damages in Bicycle Collisions

Collisions between bicycles and motor vehicles frequently result in serious injuries due to the lack of protection for cyclists. Victims may suffer traumatic brain injuries, spinal cord damage, fractures, and other life-altering conditions.

These injuries often require extensive medical treatment and may lead to long-term or permanent effects. As a result, claims in these cases often involve significant damages, including medical expenses, lost income, and pain and suffering.

Why Early Investigation Matters

Autonomous vehicle cases are highly dependent on data and documentation. Waiting too long to take action can result in lost or overwritten evidence, making it more difficult to prove fault. Early investigation allows for preservation of critical vehicle data, identification of all potentially responsible parties, and timely involvement of experts. This can significantly strengthen a claim and improve the chances of a successful outcome.

Holding Autonomous Technology Accountable for Bicycle Collisions in California

As self-driving technology continues to evolve, the legal system is adapting to address the risks it presents. Bicycle collisions involving autonomous vehicles highlight the importance of ensuring that these systems are designed and operated safely for all roadway users.

At Kalfayan Merjanian, LLP, we investigate these cases by combining legal analysis with technical expertise. Our firm works to determine whether human error, system failure, or both contributed to the collision and to hold all responsible parties accountable.

If you or a loved one has been injured in a collision involving a bicycle and a self-driving car in California, contact Kalfayan Merjanian, LLP to discuss your case. Taking early action can help preserve evidence, clarify liability, and protect your right to recover the compensation you need to move forward.