When a motorcycle collides with a car or truck in slow or stopped traffic, the defense usually tries to reframe the case around one word: lane splitting. The theory is that the rider chose a risky maneuver, the driver could not have seen them, and any recovery should be cut sharply or barred. Whether that works depends first on state law and second on the facts of speed, spacing, and signaling. Plaintiff counsel should treat it as an evidence problem, not a moral one.
Start With the Legal Status
The law on lane splitting, riding between lanes of same-direction traffic, and the related practices of lane filtering and shoulder riding, differs widely. California has long allowed lane splitting in practice and codified a definition in its Vehicle Code in 2016, allowing it when done in a safe and prudent manner, without establishing a fixed speed rule in the statute. Several other states have since enacted laws permitting some form of lane filtering or splitting, typically with limits on speed or on the circumstances, such as stopped traffic. In most states, however, the practice is either prohibited by statute or addressed only by general rules about driving within a single lane or passing on the right.
Review the current text of your state's statute before you evaluate the case. Three scenarios follow:
- Legal and regulated. The question is whether the rider complied with the statute's conditions, such as a speed differential or traffic speed cap. Fault turns on reasonableness.
- Silent or ambiguous. The defense will argue the maneuver was unlawful under lane-use or passing statutes. Responding requires careful reading of how courts have treated similar conduct.
- Prohibited. A violation can support negligence per se or at least evidence of negligence. The causation question becomes critical, because the violation must be a substantial factor in the collision.
Causation Is the Counter
Even where lane splitting is unlawful, the defendant must still show that it caused the crash. The typical scenario is a driver who changes lanes without checking mirrors or signaling, striking a rider in the space between lanes. The driver's failure to look and the rider's position are separate acts, and a jury can find that the driver's lane change, not the rider's presence, was the dominant cause. Stress that point with a clear, simple narrative: the driver had a duty to check before moving, and the rider was where a visible, expected vehicle could be.
Pay attention to the defense claim that the rider was invisible. Daytime conspicuity research, headlight modulation, and the position of the mirrors on a truck or car cab are all fair subjects for expert testimony. A reconstruction expert can place sight lines from the driver's seat and show that a check of the mirror or a head turn would have revealed the rider.
Speed Differential: The Number That Matters
When statutes or guidelines address speed, the usual theme is the difference between the rider's speed and surrounding traffic, not the absolute speed. A rider moving at modest speed past slow traffic gives drivers time to react, while a high differential shrinks that window. Gather the numbers early:
- Rider speed from the motorcycle's event data if equipped, damage analysis, or witness estimates corroborated by video.
- Surrounding traffic speed from dashcam footage, traffic cameras, navigation app data, and the other vehicle's electronic data recorder.
- Lane width and available gap between vehicles, measured at the scene.
Many modern passenger vehicles and nearly all tractor-trailers record pre-crash data, and carriers commonly keep telematics and camera footage. Send a preservation demand quickly. For commercial vehicle cases, our truck and motorcycle coverage discusses how to frame spoliation letters and electronic logging data requests.
Truck-Specific Issues
Large trucks have mirror blind spots, called no-zones, along both sides and behind the trailer. Defense arguments about unseen riders carry more weight when the driver was in a truck with limited visibility, but the driver's training and the carrier's policies bear on reasonableness. Request the driver's qualification file, any training on motorcycle awareness, and camera system footage from the cab or the sides of the trailer. Also check whether the vehicle was equipped with blind-spot detection, and whether the system was functioning.
Where the truck was changing lanes into the rider, our analysis of blind-spot duties in the auto accident category overlaps with these issues, and the evidence of a lane-change violation or missing signal is often decisive.
Comparative Fault Mechanics
Confirm the state's comparative fault regime. Under pure comparative fault, a rider found partly at fault still recovers a reduced amount. Under modified systems with a fifty-one percent or fifty percent bar, the allocation can eliminate recovery entirely, so the percentage fight becomes the whole case. A few jurisdictions retain contributory negligence, in which any rider fault may bar recovery, which makes the legality of the maneuver and the clear dominant-cause story critical.
Jury selection matters here. Many jurors have negative impressions of riders and strong views on lane splitting. Voir dire should surface those views directly and ask whether a person can follow the instruction that a rider's conduct, even if risky, does not excuse a driver's failure to look.
Practical Takeaways
- Identify the legal status of lane splitting under current state law before accepting the case.
- Build causation evidence that isolates the driver's lane change or failure to look.
- Preserve vehicle data, dashcam, and telematics quickly.
- Quantify speed differential rather than argue the maneuver in the abstract.
- Use voir dire to deal with rider bias.