Side-impact crashes at intersections are among the most injury-producing collisions in passenger vehicle accidents. The door panel is the only barrier between the occupant and the striking vehicle, and when the striking vehicle is approaching at speed, the resulting injuries frequently include thoracic trauma, pelvic fractures, TBI, and spinal cord injury. They are also among the most contested on liability: each driver typically claims the light was green, witnesses are often contradictory, and absent video evidence the jury is asked to choose between competing narratives. Building an objective liability record in a disputed-signal T-bone is what separates a pre-litigation settlement from a protracted fight.
Preserving the Intersection Evidence
The first 48 hours determine what evidence will survive. The intersection itself is a rich evidence environment: traffic cameras operated by the municipality or state DOT, red-light enforcement cameras operated by private vendors under contract with the city, surveillance cameras on adjacent commercial properties, and dashcam footage from other vehicles stopped at the intersection. All of these sources have short retention cycles.
Send preservation demands by certified mail or electronic delivery with read receipt the day you are retained, to: the municipality's traffic department for any intersection cameras; the red-light camera vendor if an enforcement camera is present; any commercial business with a camera angle toward the intersection; and any dashcam service the police report indicates was present (if a delivery vehicle, transit bus, or other commercial vehicle was stopped at the light, its dashcam footage is independently valuable). Police cruiser video from officers responding to the scene may also show skid marks, debris fields, and final vehicle positions.
Signal timing data is available from the traffic control system. Many municipalities use adaptive traffic control systems that log signal phase timing and any manual override inputs. A subpoena or public records request to the traffic department for the signal timing record for the intersection at the time of the crash will show whether the signal was functioning normally, whether there were any malfunction reports, and the duration of each phase. If both parties claim the light was green, the signal timing record either validates or contradicts one of the narratives.
Physical Evidence at the Intersection
The pre-crash tire marks, if any, are perishable evidence. Have a field investigator or accident reconstruction consultant document the intersection immediately. Pre-impact brake marks indicate the striking driver may have attempted to stop; their position and length relative to the limit line give the reconstructionist data to work backward from. Post-impact debris fields indicate the point of impact, which combined with the final rest positions of both vehicles allows reconstruction of the approach angle and relative speeds.
Event data recorder (EDR) data from both vehicles is essential in a disputed-liability T-bone. The EDR captures vehicle speed in the five seconds before airbag deployment, throttle position, brake application, and seatbelt status. If the striking driver was running the red light, the EDR typically shows no braking and maintained or elevated throttle at the impact threshold. Request both EDRs through a download protocol in discovery and have them processed by a qualified accident reconstruction expert. EDR download must be performed promptly before data overwrites can occur in later ignition cycles.
Intersection Design and Control as an Independent Theory
When repeated T-bone crashes have occurred at the same intersection or when the intersection's sight-line geometry creates predictable right-of-way confusion, the government entity that controls the intersection may share liability. Check the intersection's crash history through public records: state DOT and local traffic safety databases maintain crash frequency data by location. If the intersection has a documented history of angle crashes without remedial action, the municipality's failure to implement countermeasures (improved signage, signal phase changes, protected turn phases) may support a design or maintenance defect claim.
Government entity claims require compliance with administrative claims presentation requirements in most states, with short deadlines: six months from the date of the accident in California for most public entity claims. Missing the claims presentation deadline is typically fatal to the government entity theory. Calendar this deadline the moment government entity liability appears to be a viable theory, not after investigation confirms it.
Comparative Fault in Disputed-Signal Cases
Even with strong objective evidence, defense counsel will argue comparative fault through the entering driver's speed, distracted operation, or failure to look left before proceeding into the intersection. The counter-strategy is to establish through the reconstruction and signal evidence that the struck party had no reason to yield and that the duty to yield was entirely with the driver who ran the signal.
Speed of the struck vehicle matters in the comparative fault defense. If the struck vehicle was accelerating rapidly from the stop line, defense will argue the driver contributed by entering the intersection at an excessive speed relative to conditions. The EDR and signal timing data together will typically show whether the struck vehicle's speed at the point of impact was consistent with normal acceleration from a green light or whether there is an anomalous speed reading.
For coverage of EDR evidence and pre-crash data in auto cases, see our auto accidents practice area. Intersection design defect claims against government entities are addressed in our case law and settlements section.