This post is by Brian Rosen and Randall Gellens, participants in the ecrit working group.
Emergency calls placed by vehicles involved in a crash can provide significant benefit, especially when vehicle occupants are injured or unable to place a 9-1-1 call themselves. Sometimes called “Advanced Automatic Crash Notification” or “vehicle telematics”, the ability to automatically or manually place an emergency call when a vehicle is involved in a crash has been available for over two decades in the U.S., while the EU has a mandated system called “eCall” that is in the process of being deployed. Recently published IETF RFCs aim to expand the capabilities of such services, and to make them more broadly implementable.
Current U.S. systems are proprietary; some use non-standard in-band modems to send vehicle location and crash data from the vehicle to a call center, which then relays the information to the Public Safety Answering Point (PSAP, also known as an emergency call center). The relaying is done either by non-standard out-of-band data transmission or orally by a service center agent. Other systems place a 9-1-1 call, play a prerecorded message to the PSAP call taker, and use text-to-speech to convey vehicle location and sometimes crash data. The EU eCall system uses a standardized in-band modem to convey vehicle location and crash data from the vehicle to a specialized PSAP, which has a corresponding modem to receive the data.
The IETF has published two documents: RFC 8147 and RFC 8148 that specify how such calls operate using next-generation (all-IP) technology. Vehicles using these RFCs initiate emergency calls either manually or automatically in the event of a crash or other serious incident; the calls carry a standardized set of vehicle location and incident data. Such a call can be routed to a PSAP equipped for this, where the data can be automatically processed and displayed to a call taker at call assignment. During the call, the call taker can request that the vehicle send updated data or perform an action such as flashing its lights.
The IETF developed a generalized mechanism for making data related to an emergency call available to the PSAP along with the emergency call. This mechanism, called “Additional Data”, RFC 7852, allows standardized data “blocks” to be sent in a SIP (RFC 3261) call, either as data in the body of an INVITE message, or as a URL sent in the header which, when dereferenced, yields the data block. RFC 8148 defines a data block for the U.S. “Vehicle Emergency Data Set” developed by the Association of Public-Safety Communications Officials (APCO) and the National Emergency Number Association (NENA), while RFC 8147 defines a block for the eCall data set used in the EU. These RFCs also provide a mechanism for the call taker to request that the vehicle perform an action, such as honking the horn or flashing the lights to allow the responders to locate the vehicle.
– Brian Rosen and Randall Gellens