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Proper disabling of modern road vehicles

Technology update March 2013

Emergency services around the world are routinely called to motor vehicle collisions, and the number and diversity of motor vehicles that rescuers are called to deal with is increasing. In the past, the vast majority of cars were fueled with either gasoline or diesel fuel, and other than fuel leaks, the biggest concern rescuers were taught to deal with was disconnecting the 12-volt battery to make the vehicle “safe”. This was taught as a way to control/deplete the stored energy related to frontal airbag systems and to reduce the risk of post-crash fires. Rescuers were reasonably assured that the vehicle was disabled if this activity was completed.



How do you know if you have secured all the hazards with any vehicle that is involved in a collision? (Courtesy of wiesbaden112.de)

However, in the case of today’s alternative energy system vehicles just securing the 12-volt battery may be totally inadequate. Changes in propulsion systems have given us “silent cars”, potential high-voltage component hazards, and any number of additional never-seen-before hazards that rescuers are only beginning to learn how to respond to. These propulsion systems, coupled with the increasing number of supplemental restraint systems, and the use of higher strength steels may make it difficult for rescuers to be able to provide for an expeditious extrication of injured victims.

It is imperative that rescuers be aware of these changes and know what is inside the vehicle they are dealing with.



Today, keeping all of these concerns in mind, if rescuers follow a few simple and straightforward steps at the beginning of the extrication process, they can be reasonably assured that the vehicle will be safe to perform appropriate extrication activities in a timely and safe manner. These steps need to be in the form of a systematic approach to vehicles involved in collisions that rescuers incorporate into their daily response activities. When we say systematic, we mean approaching every vehicle in every accident the same way. This systematic approach is something that agencies should consider incorporating into their standard operating guidelines for motor vehicle collision response. So how and why should rescuers follow a step-by-step process?

Let us begin with initial scene size-up and stabilization. Rescuers need to begin by establishing appropriate incident command, safety and hazards zones, and completing a 360-degree assessment. As part of this initial assessment, rescuers should immediately place wheel chocks fore and aft at each vehicle within the 50 foot/15 meter radius safety area. This will begin to immobilize the vehicle and prevent any possible movement.

The rescue crew should then begin to immobilize the vehicle itself by activating the parking brake. This may be as simple as pulling a lever or stepping on a pedal, but more and more vehicles are using an electric parking brake mechanism. This is activated using a button that is usually located in the area of the transmission shift lever (see fig. 2).This must be completed prior to disconnecting the vehicle’s power supply since it is an electric-powered mechanism.


Figure 2: The electrically powered parking brake control in the 2012 Buick LaCrosse


The next action should be to place the vehicle’s transmission in “park” if possible. There may be instances where the transmission shifter linkage is damaged and may not permit this, but the rescue crew should attempt to get the vehicle into “park” or at the very least “neutral”. Rescuers will then want to secure the ignition by either turning off the key or pushing the ignition button (see fig. 3).

Operating an ignition button is slightly more difficult than a traditional ignition key because the status of the ignition is not obviously visible. If the occupant or a bystander has already switched off the ignition, it is certainly possible to activate the car again by pushing the button. This is why car manufactures advice also includes checking the ‘Ready-Indicator’ somewhere on the dashboard of the vehicle.

Vehicle manufacturers also advise rescuers to remove the key or key fob from the vehicle. The reason for this advice is to avoid accidental restart of the vehicle. Therefore no time should be wasted to search for a key or key fob if it is not obviously visible in the vehicle as smart key systems may also be carried everywhere in the interior (drivers pocket, handbag etc.). As soon as the deactivation process is complete, accidental restart of the system is not possible anyway.


Figure 3: Ignition button on a 2012 Toyota Highlander Hybrid. These will be found on many vehicles, not just alternative power vehicles.


Shutting off the ignition of a vehicle is an often-underestimated safety factor. The fuel pump will stop to work, high voltage relays used on the high voltage batteries of hybrid- and electric vehicles will open, electromagnetic shut-off valves used on natural or propane gas tanks will close and the supplemental restraint system (“SRS”) control unit will lose its power and the drain time of the built-in capacitors will start. While some of those measures may already have been triggered by the SRS control module because of the crash detection it is important to manually switch off the ignition to make sure the systems are really disabled. Remember that not all sorts of accidents can be detected by the SRS system.


If the ignition cannot be switched off, just disconnecting the 12-volt battery will probably not disable a hybrid or electric vehicle. Research shows that even after disconnecting the 12-volt negative battery cable, there are vehicles that will remain powered if the ignition is still in the “on” position. The vehicle can actually be driven with the 12-volt disconnected. Two examples of vehicles that this will occur with are the Mitsubishi i-MiEV and the Chevrolet Volt (US)/Opel Ampera (Europe).



Figure 4: The 12-volt battery of this Chrysler Sebring is located in the wheel well of the vehicle. Accessing the battery is a challenge when the wheel is mounted and virtually impossible with crash damage. However, the battery ground cable can be disconnected


Figure 5: The 12-volt battery of this GMC Acadia is located in the floor of the vehicle under the passenger’s seat. The screenshots from the Crash Recovery System show how it can be accessed.


The reason for this is that, in the simplest of terms, the vehicle only needs its 12-volt battery to open the high voltage relays and after that, the vehicle is powered entirely from the high voltage battery pack. As long as the ignition remains “on” the vehicle is drivable and all systems including the SRS system are operational.

Rescue companies may also want to consider activating a vehicle’s four-way/emergency flashers as part of their initial vehicle assessment. This will give an indication of the status of the vehicle and will serve as another method of determining that the vehicle has been de-powered, as well as alerting all rescuers on the scene to the status of the power supply. As stated previously, just because the 12-volt power supply is disconnected, does not mean the vehicle is de-powered. Many late model vehicles will activate the emergency flashers automatically when an accident has been detected. The described procedures only take few seconds and should be carried out before patient treatment should start inside the vehicle.

The next step should be to secure the vehicle’s power supply, which may be connected to a conventional 12-volt battery or eventually a high-voltage battery. If the vehicle is only equipped with a conventional 12-volt system, the biggest challenge in respect to disabling is to locate the battery or batteries of the vehicle. This is why the incident commander may want to consider acquiring details about the vehicle equipment using a vehicle information system such as the Crash Recovery System (CRS). This system provides a detailed view of all rescue relevant vehicle equipment such as the battery, airbags, reinforcements and propulsion system components. The location of the 12-volt battery will be shown, as well as instructions on how to get to the battery will help emergency responders to even locate batteries that may be hidden in the trunk, under seats or in the wheel well of the vehicle (see fig. 4 and 5 for examples).The CRS also provides assistance in locating the battery ground cable if it can be accessed easier than the battery itself.

The difficulties in locating or accessing the 12-volt battery on late-model vehicles often leads to the discussion as to whether it is generally necessary to disconnect the vehicles power supply. The manufacturer’s emergency response guides are quite clear in this respect and advise to do so. Being realistic, every emergency responder knows that there may be occasions when the battery cannot be accessed because of its location or the position of the vehicle. Nevertheless, remember that shutting down the vehicle is just as important for everybody’s safety as with every other machine emergency responders have to work on, regardless what the ERG’s say. Many things can, and already have gone wrong, when a machine or vehicle has not been properly disabled. There are enough cases where vehicles or machines suddenly started to move or work, where arcing and sparking caused fires, or where airbags deployed during extrication efforts.

If the vehicle is also equipped with an alternative power source such as a high-voltage battery, safely disabling the complete system may become even more challenging as some vehicle manufacturers advise rescuers to follow special disabling procedures in their Emergency Response Guides. While some manufacturers advise emergency responders to switch off the ignition and to disconnect the 12-volt battery of the vehicle some vehicles require additional action. One example that demonstrates the differences in shut down procedures is the Buick LaCrosse equipped with “e-Assist”. In addition to switching off the ignition, the manufacturer advises emergency responders to cut two marked cables in the engine compartment, in a recommended order, to disable the vehicle (see fig. 6).



Figure 6: Screenshot of the 2012 Buick LaCrosse 12-volt battery cables. Cables should be cut in the manufacturer’s recommended order.


Figure 7: The Toyota Prius ERG advises to pull certain fuses in addition to disconnecting the 12-volt battery.


Most Emergency Response Guides and the Crash Recovery System also provide information for those instances when the ignition cannot be switched off on an electric, hybrid or alternative powered vehicle. As stated before, disconnecting the 12-volt battery only may not be enough to disable those vehicles in such a case. That is why the vehicle manufacturer advises emergency responders to pull certain fuses, cut specially marked cables, remove the service plug, or do similar things in their guidelines. An example of this is the Toyota Prius (now in its third generation). If the ignition cannot be switched off, the manufacturer-provided ERG advises rescuers to pull certain fuses from the fuse box. This is in addition to disconnecting the 12-volt battery (see fig. 7). Another example is the pure-electric Nissan Leaf. If neither the ignition button nor the engine compartment is accessible the manufacturer advises emergency responders to remove the service disconnect switch (service plug) with appropriate PPE (see fig. 8).


Figure 8: If other shut down procedures cannot be accomplished in the Nissan Leaf, the manufacturer advises to operate the high-voltage disconnect. The access panel to this switch is located in the center of the rear floorboard area and requires some simple hand tools to remove the access panel cover.


Knowing the right measures to disable the vehicle is therefore very important. As it is impossible to remember all the vehicle specific methods, a vehicle information system such as the Crash Recovery System can provide all the necessary info. Other than the Emergency Response Guides, the CRS carries all information in a standardized format to allow quick orientation and selection of the right disabling procedure.

As the vehicle shut down operations progress, outside rescuers need to make sure to check with the interior rescuers that all electrically powered beneficial systems for the rescue have been used before actually disconnecting the battery or disabling the vehicle with the procedure set by the vehicle manufacturer. Moving electrical seats, lowering windows, opening the rear hatch or the roof window may all be electrically controlled actions that may make rescue measures and extrication easier.

After all of these steps are completed, the vehicle should be able to be safely approached to begin extrication efforts. Remember, throughout the extrication operation rescuers will still need to continuously assess the vehicle for additional hazards or challenges to the rescue operation, such as airbag stored gas inflators, high-strength steels, fuel or energy system components, etc. Another important point to remember is that after all patient extrication activities are completed, the incident commander should make other responders (police investigators, tow truck operators, etc.) aware of the make/model of the vehicle and what depowering and other safety activities were completed by the rescue service. In some cases, vehicle manufacturers require additional de-powering procedures to be performed by dealer technicians or other specially trained service personnel. It is also important to remember that the safety of other responder groups is just as important as the safety of rescuers.

Rescuers need to keep one other important point in mind as they are performing the various shutdown procedures. Vehicle manufacturers are producing so-called “emergency response guides”, especially for electric, hybrid, and other alternative powered vehicles. Each of these ERG’s details the manufacturers recommended procedure for securing the vehicle. The unanswered question is what will the liability be to rescuers for failing to follow these procedures, especially if something happens and/or someone is hurt? If rescue companies have tools available to know the proper procedures, follow the manufacturer’s guidelines, and still stay trained in and follow the proper procedures, that question will never have to be answered. In closing, keep in mind that throughout the article, several different vehicles have been used to highlight examples of many of these steps and the differences that will be encountered in the response to motor vehicle collisions. There are hundreds of makes/models of vehicles on the road today throughout the world, and no one rescuer, or even rescue company, can be knowledgeable on every single vehicle that may be encountered. Again, this it is why it is imperative to use a systematic approach at all motor vehicle collisions, as well as using the most appropriate resources to determine what is inside.


JJörg Heck is a 15-year veteran of the volunteer fire service in Mainz (Germany). He is the extrication specialist for Moditech Rescue Solutions B.V., which developed the Crash Recovery System. He also instructs vehicle rescue and is a well-known instructor in new vehicle anatomy. He has been involved in a number of books and articles on extrication and new car technology related topics. Jörg can be reached by email at jorg@moditech.com. Eric J. Rickenbach ("EJR") is a 30-year veteran of the volunteer emergency services from Rehrersburg, Pennsylvania (USA). He is a rescue instructor specializing in vehicle rescue, with particular interest in new car construction, energy, and safety systems. In addition to teaching and research, Eric is active in several vehicle rescue-related committees. He can be reached by email at ejr@rescuetechs.com


Originally published in T-Rescue Magazine (www.t-rescue.com), Issue 63, 2012