In June 2025, Steven Ruggiero learned firsthand what it means to be at the mercy of his e-mountain bike’s motor control system. He was riding his Turbo Levo in Eco mode on the Alpine Trail near Oakridge, Oregon, when his rear wheel suddenly spun out of control, as he later described. He crashed and broke seven ribs. A court is now set to determine who is responsible: Ruggiero or the manufacturer. But how do you figure out what really happened during a crash when the most important witness is a black box? What does the rider actually rely on in this situation?

When the system intervenes while riding

Modern e-mountain bikes don’t just transmit power; they also control when and how the assistance kicks in. A network of sensors measures cadence, torque, and incline. Based on these signals, the system calculates when and how much the motor should assist. The rider selects the mode, pedals, and steers. The e-bike then continuously regulates the actual level of assistance on its own.

Specialized also incorporates a feature known as “overrun”: If the rider stops pedaling, the motor continues to run briefly before the assistance ends. The standard limits this: After the last pedal stroke, the assistance may continue for no more than two meters. This helps on technical sections—over roots, steps, or tight turns—where half a pedal stroke is often not enough or where continuing to pedal is briefly impossible. This makes the situation tricky: Overrun is not a fault, but an intentional aid; yet it blurs the line between a burst of power triggered by the rider’s pedal stroke and a burst of power that the system continues on its own.

Once riders get used to this assistance, they often rely on it unconsciously. This has been well documented in research on autopilots and driver-assistance systems: the more reliable a system appears, the less humans tend to question it. On e-mountain bikes, too, riders constantly rely on motor assistance, the use of which the system partially regulates on its own. As long as everything works, this assistance remains almost invisible. But even the best motor control system is no guarantee of absolute flawlessness. Things only get tricky when, after a crash, it remains unclear whether the system played any role at all at that moment.

Sold before anyone could check it

In the Ruggiero case, that’s exactly what became the problem. Ruggiero is seeking damages because he holds the motor’s after-run partially responsible for his crash. Specialized disputes this. Both sides were nevertheless close to reaching a settlement without a court ruling, but before it could be finalized, Specialized’s attorney demanded the return of the bike involved in the accident for examination. Ruggiero had already sold it to a friend by then. As a result, the key piece of evidence was no longer readily available, and Specialized alleged obstruction of justice. In May, a judge refused to enforce this settlement. According to its answer to the complaint, Specialized denies the allegations and cites, among other things, rider error and unauthorized modifications to the e-bike.

Even if the e-mountain bike were still available, it remains unclear whether it could have truly resolved the dispute. Motor control systems are not designed to accurately reconstruct a crash after the fact. Bosch and other manufacturers store operating data and error codes for the repair shop, but not the exact force trajectory in the second leading up to a crash. The situation is different for cars: Since 2024, every new car in the EU must have an event data recorder that captures precisely those seconds. This requirement does not yet apply to bicycles and e-bikes. Bicycle experts, such as the German assessor Dirk Zedler, therefore reconstruct crashes based on fracture patterns, deformations, and marks on the material—not on software logs. If the frame remains intact, the cause often remains unclear.

Yet the drive system is officially considered safe. For pedelecs, the European standard requires that, in the event of a dangerous malfunction, the control system cut off power to the motor without creating a new hazard, and that the drive not restart automatically afterward. This does not guarantee that no errors will occur, but only that the system will shut down safely in the event of a fault.

When the Blame Falls on the Rider

If it cannot be determined whether the motor control system played any role at all in a crash, suspicion almost automatically falls on the rider. Anthropologist Madeleine Clare Elish calls this a “moral crumple zone”: When the rider and the machine share control, but it remains unclear who was responsible for what at the decisive moment, the blame usually falls on the rider because they are the only one who can be questioned. There is often no clear evidence regarding the role of the motor control system.

Liability law is now responding to this as well. Until now, anyone who suffered harm due to a defective product had to prove on their own that a defect existed and caused the damage. In the case of an engine control system that can hardly be inspected from the outside, this is nearly impossible for those affected. A new EU directive is lowering this hurdle. If an injured party is unable to prove the defect due to technical complexity, in the future it may be sufficient—under certain circumstances—to demonstrate a high probability that the product was defective or contributed to the damage. If a manufacturer fails to disclose its documentation, this may be used against it. The directive will apply starting in December 2026 to products newly placed on the market, including software. In Switzerland, the old standard from 1994 still applies: Anyone filing a lawsuit must prove the defect and its cause themselves, just as the EU also required until 2024. Although an adjustment is being called for, it has not yet been initiated.

The Ruggiero case is not proof that e-mountain bikes are getting out of control. They help regulate the assistance and thus directly influence how riders ride. After a crash, however, their role often cannot be clearly established. In such cases, software, accident forensics, and liability law intersect directly. It remains unclear how manufacturers, riders, and courts should deal with a system that intervenes but remains a “black box” in the event of a dispute.