Physical Address
304 North Cardinal St.
Dorchester Center, MA 02124
SAE J1698-1: Event Data Recorder Output Data Definition
Overview of the Standard
The SAE J1698-1 standard defines the output data elements for Event Data Recorders (EDRs) in vehicles. It establishes a common set of data elements, event definitions, capture triggers, and accuracy requirements to ensure consistent and reliable crash data recording. This recommended practice is essential for accident reconstruction, vehicle safety analysis, and regulatory compliance. By standardizing the way EDR data is recorded and reported, the standard enables cross-manufacturer data consistency and supports the advancement of automotive safety systems.
Event Definitions and Minimum Data Set
The standard specifies several event types: Front/Side/Rear Impact, Pedestrian Impact, and Rollover. Each event type has a clearly defined beginning (time zero) based on thresholds such as longitudinal delta-V or roll angle. The Data Capture Requirements describe the recording duration and the handling of multiple events in a single record. The minimum data set includes fundamental parameters that must be captured to support crash analysis:
| Data Element | Description |
|---|---|
| Longitudinal Delta-V | Measured change in velocity along the vehicle’s longitudinal axis during the event |
| Maximum Recorded Longitudinal Delta-V | Highest delta-V value recorded during the event |
| Time to Maximum Recorded Delta-V, Longitudinal | Time from time zero to the maximum delta-V point |
| Speed, Vehicle Indicated | Vehicle speed as indicated by the speedometer |
| Engine Throttle Position (or Accelerator Control Position) | Percentage of throttle opening or accelerator control input |
| Service Brake, On and Off | Brake pedal status (applied or not applied) |
| Ignition Cycle at Event | Number of ignition cycles at the time of the event |
| Ignition Cycle at Imaging | Number of ignition cycles when the data record is imaged |
| Safety Belt Status, Driver | Driver’s safety belt buckle status |
| Occupant Protection System Warning Lamp Status | Status of the occupant protection system warning lamp |
| Occupant Protection Device Deployment Time (Driver & Passenger) | Time of first stage deployment for frontal air bags |
| Multi-Event, Number of Events | Number of events stored in the recording |
| Time from Event X to Y | Time difference between two specific events in a multi-event scenario |
| Event Data Recording Complete | Flag indicating that the data recording has been finalized |
Implementation Insights and FAQs
🛠️ Engineering Design Insight
When implementing an EDR compliant with J1698-1, pay close attention to the definition of time zero for each event type. The delta-V threshold for impact events may differ from the criteria used for pedestrian impact or rollover events. Properly handling the data element status flags (available, not available, invalid) is critical to avoid misinterpretation of recorded data. Use the standard’s exact naming and units for data elements to maintain consistency across manufacturers and ensure interoperability.
⚠️ Common Pitfall
Confusing the beginning criteria for pedestrian impact events with those for frontal impacts can lead to improper data capture. Always refer to Section 4.2 of the standard for pedestrian-specific definitions and trigger conditions. Additionally, ensure that data element availability status is always set correctly to prevent misanalysis.
Frequently Asked Questions
What is the recording duration for an impact event?
Per the standard, the duration is defined from the beginning of the event (time zero) until the end when specified conditions are met, typically covering pre-event and post-event data windows as detailed in Section 4.
How should pedestrian impacts be differentiated from other impacts?
Pedestrian impact events have specific trigger criteria, such as detection of a pedestrian collision via sensors, ensuring they are recorded as a distinct event type separate from front/side/rear impacts.
What are common mistakes when implementing J1698-1?
Common pitfalls include confusing the beginning criteria for different event types, failing to properly mark invalid or unavailable data elements, and not adhering to the recommended naming conventions and units for data elements as defined in the standard.
How are multiple events managed in the data record?
The standard defines multi-event management through the Number of Events and Time from Event X to Y data elements, allowing for sequential tracking and time correlation between multiple events in a single recording session.
