Letter Mail Controlled 11/5/2003 8:08:51 AM MC# 2030533 - From Jack Pokrzywa, Manager, Ground Vehicle Standards: It should be noted that the SAE does not issue "requirements" in the strict sense of this word, but rather issues voluntary "Standards" and "Recommended Practices" that reflect the consensus of interested members regarding a given technical subject. Notwithstanding this clarification, we understand the NTSB’s recommendation to reflect a desire to see the issues raised in the subject letter addressed by an SAE Standard or Recommended Practice.
Currently, SAE is not developing an EDR Standard or Recommended Practice for heavy-duty vehicles, and therefore is not in a position to comment on the implications of the subject recommendation for such vehicles. However, the SAE Vehicle Event Data Interface (VEDI) Committee has developed a Recommended Practice for EDRs on light-duty vehicles, SAE Ji 698, and is in the process of developing another Recommended Practice specifically addressing a download protocol. We have opted to classify both documents as Recommended Practices rather than as Standards in recognition of the fact that EDR technology is still
developing and there is therefore a lack of adequate consensus to support a Standard at this time. The current scope & purpose statements for J1698 is as follows: 1. Scope
This recommended practice aims to establish a common format for displaying and presenting crash-related data recorded and stored within certain electronic components currently installed in many light-duty vehicles. This recommended practice pertains only to the post-download format of such data and is not intended to standardize the format of the data stored within any on-board storage unit, or to standardize the method of data recording, storing, or extraction. Historically, crash data recording technology in light-duty vehicles has developed and evolved based on differing technical needs of manufacturers and their customers without industry standards or government regulation. As a result, wide variations currently exist among vehicle
manufacturers regarding the scope and extent of recorded data. For this reason, this recommended practice is not intended to standardize or mandate the recording of any specific data element or to specify a minimum data set. Rather, it is intended to be a compilation of data elements and parameters that various manufacturers are currently recording, as well as those elements reasonably predicted to be recorded in the foreseeable future, and to establish a common format for display and presentation of that data so recorded. This version of the recommended practice is limited in application to vehicular data recorded in single frontal impact events with a Delta-V of 6.4 km/h (4 mph) or greater. Provisions for multiple-impact events may be included in the next version. Side-impact and rollover events may be addressed at a later time.
1.1.1 Limitation and Justification of Scope
126.96.36.199 Post-Download vs. Pre-Download Formatting
The scope of this version of recommended practice is deliberately restricted to providing post-download formatting guidelines, only. This restriction is to avoid imposing constraints on the type of data recorded, the method of gathering and storing data, and the pre- and/or post-processing of data that may be used by various vehicle/device manufacturers as a matter of proprietary design. This recommended practice suggests, in essence, if a manufacturer implements event data recording as defined by the scope of this document, then it ought to make a copy of the recorded data available in a generic format that enables comparative use of
the data by any interested entity that has permission to access it. As noted above, vehicle event recording is a fairly new automotive feature for which there is a variety of applicable uses and implementation strategies in existence. Therefore it is reasonable to assume that the current nascent state of the technology precludes competent assessment of available options necessary to identify an optimal solution. The Committee further recognized that, given the still-questionable social acceptability of on-board data recording devices, it also lacks the appropriate authority to effectively set a policy on such devices, and has therefore avoided
specific recommendations concerning whether event data recorders should be equipped on motor vehicles, and whether, when implemented, a particular type, quantity, and manner of data collection should be used.
188.8.131.52 Single Frontal Impact Events vs. Multiple Frontal Impact and Non-Frontal Impact Events
The current version of the subject recommended practice specifies that an "event" for the purposes of this document is defined as a single frontal impact resulting in a change in velocity of more than one half mile per hour in a 20 millisecond time period. This threshold approximately correlates with the threshold used by most airbag firing algorithms for "wake-up" purposes (i.e., for the purposes of beginning the sequence of acceleration-based calculations that may lead to the firing of one or more pyrotechnical restraint device). It was chosen because light-duty manufacturers already equip motor vehicles with deployable restraints triggered by
frontal impacts, and the technology used to do so is mature, and therefore fairly similar among manufacturers. Due to a variety of recording strategies, some events may not result in recorded data. The threshold for recording event data is left to the discretion of manufacturers. In the next version of this document, provisions for multiple frontal events may be included. During subsequent reviews, provisions for non-frontal impact events may be added if the state of technological maturity supports a common definition for such events.
Vehicular event data recording and extraction has several potential uses. These include diagnostic and operational information of the on-board occupant protection system, crash reconstruction, and improved highway safety. Collection of various types of data for a variety of commercial and non-commercial uses is of significant interest of many entities, most of which are not mentioned in the statement of the Purpose. A standard format for vehicle event data output will help facilitate these uses, and possibly more, by improving the availability and efficient use of the extracted data. The judgment on the appropriateness of any particular use of recorded data is beyond the scope and purpose of this recommended practice therefore the
Committee passes no judgment on that issue.
Current light-duty vehicle electrical/electronic architecture does not typically support real-time data recording and synchronization capability. Because the focus of this effort is on light-duty vehicles, only, the data parameters and collection strategies considered have been tailored to the prevailing technology and vehicle architecture common to this platform. As noted in the Scope and Purpose statements above, the SAE effort has carefully limited its focus to codifying a common output format for data already collected by vehicle manufacturers, or under consideration for recording in the foreseeable future. Specifying real-time recording and
synchronization parameters would amount to ".. .imposing constraints on the type of data recorded, the method of gathering and storing data, and the pre- and/or post-processing of data that may be used by various vehicle/device manufacturers as a matter of proprietary design" in contradiction to the scope of J1698 (see section 1 .l .l .l , above). The SAE VEDI Committee has therefore decided not to address the subject NTSB recommendation in the current version of the Recommended Practice J1698. However, we will retain the recommendation in our Committee files and consider it in the future as this document is revised over time to reflect changing vehicle architectures and data collection practices.
If you would like to obtain more technical details regarding SAE’s efforts in the vehicle Vehicular
Event Data Interface, please contact me at 248-273-2460.