GPS And Accident Response: Phenomenal Times


Posted on 27th October 2015 by admin in Tech


gpsMinnesota’s Mayday Plus project combines GPS with in-vehicle accelerometers to automatically relay not only accident location but also crash severity data. The system intelligently routes this information, based on location and type of emergency, directly to public safety dispatchers in the appropriate jurisdiction. Emergency crews can then respond more quickly and with better preparation for the type of accident and probable injuries.

The time between an injury’s occurrence and the provision of emergency medical care can make the difference between life and death in trauma cases. Emergency medical response can save the majority of critically injured patients, if it can reach them and get them to. appropriate care facilities quickly enough. In rural traffic incidents, obtaining accurate location information can consume precious minutes, reducing the time physicians have to save a victim’s life.

Minnesota’s Mayday Plus project has developed and operationally tested a special emergency response communications system through the state highway patrol and emergency medical dispatch centers. The system automatically provides collision notification, using GPS to furnish location and other in-vehicle sensors to sense and transmit crash severity data. The Mayday Plus system relays vehicle location information, direction of crash impact, the vehicle’s final resting position, and the change in velocity during the crash. It intelligently routes this data, based on location and type of emergency, directly to the dispatchers in the appropriate jurisdiction. After transmission, the system automatically opens a direct voice connection to passengers in the car.

Traffic on rural Minnesota roads accounts for 30 percent of miles travelled, but 70 percent of the state’s accident fatalities. National statistics tell a similar story, demonstrating the need for improved accident response in rural settings, where single-vehicle and run-off-the-road crashes can go undetected for hours, and where accurately locating and quickly dispatching assistance presents difficulties.

Cellular phones provide a tool for vehicle occupants to quickly report roadway incidents. However, this method does not currently provide accurate location data to emergency responders, who must rely on the caller’s ability to give accurate information. Further, it requires a conscious individual to make a call. In a serious incident on a deserted rural highway, the victims may be unconscious, and passers-by rare. It could take several hours to notify the appropriate emergency services for the jurisdiction.

Other current commercial Mayday systems use airbag deployment sensors to detect and send notification of crashes, but these cannot provide information on the nature or severity of the crash, and the urgency of sending assistance.

Mayday Plus, a public-private, multiple-organization partnership, developed and tested a response system integrating existing emergency response agencies with the rapidly growing commercial market of in-vehicle Mayday products and services. The project prepares for scalable deployment of a self-sustaining automated accident location and collision severity notification system. The project encompassed system design, implementation, onsite testing, training, and a sixmonth operational test phase using 50 vehicles from August, 1999 through January, 2000. Mayday Plus demonstrates the technical feasibility of such a system, and identifies and seeks to resolve jurisdictional issues involved in emergency response.

System Description

The Mayday Plus system targets a direct voice and data link from the accident vehicles to emergency dispatchers in southeastern Minnesota. The system includes:

* the in-vehicle equipment suite shown in Figure 1, comprising the In-Vehicle Module (IVM), a cell phone handset and transceiver, a back-up battery, and associated antennas

* dispatch interface workstations at Minnesota State Patrol District 2100 (MSP 2100), Mayo Clinic Emergency Communications Center (MECC), and the Rural Metro National Message Center (NMC)

* data and voice communication links (shown in Figure 2) between the in-vehicle equipment, NMC, MSP 2100, and MECC via the gateway communications system.

Cell phone. The IVM controls the cellular transceiver and handset via a serial control channel. The handset can be directed to operate as a normal hand-held unit, or can be operated in a hands-free mode directing the audio-out to the larger speaker underneath the keypad, and taking incoming audio from the microphone above the LCD display.

The system software maintains control of the handsfree mode; when the Mayday Plus system detects an accident, it connects the car’s occupants to the dispatcher in hands-free mode regardless of the handset’s position. If the IVM detects a crash while the handset is in use, it overrides the call in progress to establish the Mayday Plus connection — unless the call in progress is already a 911 call.

Battery. The IVM keeps the back-up gel-cell lead-acid battery constantly charged so that it can provide enough emergency power for collision reporting and an extended duration phone call or two, should the accident disconnect or destroy the car’s battery.

IVM. Packaged in a rugged aluminum housing, the IVM contains a high performance (16 bit processor, 13.8 MIP) digital signal processor (DSP), three orthogonally mounted micro-machined accelerometers, an analog to digital converter (ADC), a single-chip modem, a 12-channel GPS receiver board, power conditioning circuitry, and a nonvolatile flash memory (128 kBytes, expandable to 1024 kBytes) to store detailed crash event time histories.

DSP. The IVM uses very DSP-intensive detection and sensor conditioning algorithms; many computations are tight loops of multiplyintensive convolutional equations. The 16-bit fixed-point DSP has a program data bus and a data data bus (internally), and also controls the peripheral devices and telematics sequencing.

The IVM has as much RAM available to it as the DSP can directly address. Since the program and data data busses are multiplexed into a single data bus for external RAM access, the IVM maps both program RAM and data RAM into the same physical set of devices: three 32k by 8-bit RAM chips.

The IVM stores many of its parameters, much of its operational code, and all of the data collected during a collision in flash memory.

Serial I/O. The IVM requires six serial ports: two for the modem and one each for communication with the GPS receiver, the handset, the transceiver, and the diagnostic port. The diagnostic port is used to upload the program and parameters into the IVM, including the transformation matrix that allows the crash algorithm to account for IVM installation orientation within the vehicle. An external Reference Correction Unit used during installation provides the transformation matrix. The diagnostic port also uploads measured event histories.

Modem and audio multiplexing. The IVM uses a singlechip modem, initiating calls at normal V.23 originate baud rates of 75 baud transmit, 1200 baud receive. Since the IVM will transmit the preponderance of information and reception is required only for commands and verification, after connection the channels are immediately reversed so that the IVM transmits at 1200 baud, receives at 75 baud.

GPS Receiver. The system utilizes a 12-channel GPS receiver on a small PC board. This “daughter” board is mounted on the in-vehicle module board and connected via ribbon cable. The GPS signal provides the vehicle latitude, longitude and speed.

Sensors. Three orthogonal accelerometers mounted on the in-vehicle module board record vehicle motion in the X,Y and Z directions. These accelerometers are calibrated to align with the vehicle coordinate system (longitudinal, lateral and vertical directions) during installation.

Digital Signal Processor (DSP). The DSP continuously calibrates and reduces the sensor data, processes the information to recognize a crash, assembles an emergency message, initiates the data and voice cellular communications, and transmits the message. The accelerometer outputs are anti-alias filtered and sampled at 1440 samples per second with an onboard 12-bit analog-to-digital converter. These data are then decimated and filtered to 180 samples per second at 60 Hz.

The system samples the GPS signal at a one per second rate, and incorporates GPS location and speed information into the emergency message.

Power Regulation.

Power for the IVM comes from the automobile’s power, is diode-isolated, and switches automatically between car power and back up battery as needed. After a series of protection and filtering components, a switching regulator converts the voltage to 5V Power for the transceiver and handset comes from the diode node, switched under computer control using a field effect transistor. The battery is float-charged whenever the ignition line is on.

Logic flow. Figure 3 provides a schematic description of the logic flow among in-vehicle components. The crash detection algorithm processes the acceleration data in real time and identifies a crash based on direction-dependent injury producing thresholds of vehicle acceleration and velocity change. The crash characteristics of velocity change, principal direction of crash force (PDOF), rollover, and final rest position are calculated and stored in permanent flash memory along with the complete triaxial acceleration time-history Following the crash event the acceleration data are analyzed and crash parameters determined. The system also obtains vehicle location at the time of crash, expected error in the vehicle location, and vehicle tracking for the preceding 10 seconds.


The system assembles all this information into a Mayday data packet crash message and initiates the cellular transceiver to call the NMC within one minute of the crash. It sends the message, including the cellular telephone number of the in-vehicle equipment, and date and time the device initiated the request. When the NMC has successfully received all data, the cellular call is switched to voice and the vehicle occupants can talk with Public Safety Answering Poing (PSAP) dispatchers in a hands-free mode. This system differs significantly from currently available airbag-initiated Mayday systems in that it provides measures of crash severity

The gateway communications system routes calls and data intelligently based on the caller’s location and emergency response jurisdictions. This feature makes it unique from other Mayday systems, providing a direct link to public emergency responders and giving the identified agency useful emergency-related data including crash severity parameters. Data from the IVM initially goes to the NMC, which automatically and immediately routes it to MSP 2100 and MECC, when the crash occurred within the MSP and MECC jurisdictions.

If the location information fixes the crash position outside the Minnesota jurisdictions — wherever the location may be, nationwide — the system alerts MNC operators, pops up the relevant local map showing location, identifies the appropriate PSAP for that location and provides the phone number. NMC operators can then contact that PSAP, relay the information, and connect the vehicle directly to that PSAP. This feature gives the Mayday Plus system national rollout capability.

Operational Tests

The operational test phase ran from August 16, 1999 to January 30, 2000, analyzing performance of the IVM, computer software interface applications, communications, and system routing procedures. The tests took place in southeastern Minnesota, location of both the MSP 2100 and the MECC in Rochester. Communications from the vehicles used an established cellular telephone infrastructure.

As this testing took place before the turnoff of selective availability (SA), the GPS system produced accuracies of approximately 100 meters, the best available at the time of the test. Of course this performance will improve in the post-SA environment, and will need to in more difficult location environments.

The system produced a near 100 percent success rate of message routing: it delivered all messages per spec, that is, to the correct PSAP jurisdiction. We experienced some problems with time stamps due to a software problem. The problem was not detected until after the test and was therefore not corrected.

Collision Data

The system gateway records the PDOF the vehicle’s rollover condition, and the vehicle’s final resting position, and displays this information graphically on the call screen. All three pieces of data provide useful information for emergency management personnel in determining the collision’s potential severity, as well as the appropriate resources to dispatch to the scene.

During the Minnesota tests we instrumented 50 vehicles. In addition to these test vehicles, suitcase testers generated synthetic crashes and calls, testing message routing and the effectiveness of the information on PSAP operations.

A sister field operational test in western NewYork had already tested in-vehicle crash sensing equipment. That automatic collision notification (ACN) field test, sponsored by the National Highway Safety Administration (NHTSA), instrumented more than 700 vehicles over several years, and experienced 70 crashes, 48 below threshold and 22 above threshold.

While we configured the suitcase testers to produce only “simple” head-on collisions with a PDOF of 12, no rollover and a final resting position of upright, they provided adequate data for testing the PSAP routing and the system’s data display capabilities.

The PDOF information enables dispatchers to determine if the vehicle had a head-on collision, a side-impact collision, or an impact from behind.

The final vehicle resting position provides information dispatchers can use to determine if the vehicle rested on its roof, side, or upright at the end of the crash.


The Mayday Plus project developed a gateway for routing Mayday calls throughout Minnesota, a gateway capable of receiving and routing data and voice calls to PSAPs based on type of call and PSAP jurisdictions. It routes data to all PSAPs that may become involved in the call and sends voice to the PSAP responsible for coordinating the call.

The project developed a networked software and a user-friendly graphical user interface (GUI) to support coordinated teams of dispatchers working within and across emergency response centers in southeastern Minnesota.

A national message center (NMC) handled and routed Mayday Plus calls 24 hours a day, 7 days a week, staffed by certified emergency medical dispatchers, with a Mayday Plus Gateway and equipment for receiving and routing data and voice portions of calls.

The Mayday Plus project attempted to closely match pre-existing emergency protocols and procedures. This required interagency cooperation between MECC and MSP, emergency responders, and other local PSAPs in the test area. Institutional issues encountered during the operational test included agency concerns about loss of jurisdiction, procedural impacts, and increased workload. Working through these concerns in the context of the test began to resolve underlying institutional issues, as those involved saw the benefits of Mayday technology and adapted existing procedures to work with the new Mayday Plus functions.


Test results show widespread user acceptance. Dispatchers found the Mayday Plus system easy to learn and use — not entirely surprising since they had significant input into its design. The location information of successful test calls proved sufficiently accurate for dispatch of emergency services in the test area. Post-SA location accuracy will improve in the future.

Conclusions of the Minnesota Mayday Plus and the NewYork ACN projects include:

In-Vehicle Technology Works. All critical functions of crash sensing, location determination, telematics data communications, and mapping worked together reliably to give PSAPs time-critical crash information. The system provided accurate location and distinguished between crash events and non-crash events. Finally, the equipment survived crashes.

PSAPs Need Mayday Data. The tests demonstrated the feasibility of routing Mayday data to PSAPs for immediate display following emergency events. PSAP dispatchers could put the data to good use, especially the accurate location immediately following the emergency event. Most locations have wireless communications infrastructure in place, although gaps occur in cellular coverage in some rural areas. Building connectivity with commercial Mayday providers constitutes the next key step.

Institutional Barriers Remain. Fears about increased workload and concerns that less-tested systems will replace existing working systems and procedures constitute barriers to national deployment.

When Installed, ACN Works. Mayday systems can save lives only when people purchase them for their vehicles. This requires a commercial model at an affordable price. The continued sales growth of systems like OnStar and Lincoln RESCU indicate Mayday systems’ commercial viability. Challenges include issues of liability and privacy, and better connectivity between commercial Mayday providers and PSAPs.

ACN Reduces Response Time. The tests provided PSAPs with crash notification in less than a minute. This speed together with accurate map display location expedited response.

Next Step

While the Mayday Plus System demonstrated the feasibility and benefits of linking in-vehicle Mayday systems with the emergency response professionals in PSAPs, a key next step must be taken. Government and industry organizations should develop and pursue an approach that can lead to national deployment. This will involve employing accepted communications standards and protocols to allow connectivity with commercial Mayday providers and integration with the existing 9-1-1 call routing system. Efforts now underway build on the technical successes of ACN and Mayday Plus and the market successes of commercial Mayday systems to achieve national Mayday solutions that can save lives on our highways.

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