The first two of the three electromagnetic pulses (EMPs) emitted during a nuclear explosion are by far the briefest. The first pulse has a duration of nanoseconds; the second lasts only microseconds. Both, especially the first, can permanently damage solid-state electronics.
Electronic devices can be protected from an EMP by storing them in a Faraday shield, an enclosure made entirely of an electrically conducting metal, plastic, or fabric. I showed how to make your own Faraday pouch in Make: Volume 72.
Protecting vehicles is another matter, for they are much larger. Fortunately, the metal from which most cars are made provides some EMP protection. The U.S. Congressional EMP Commission subjected 37 running and nonrunning cars to EMP up to 50,000 volts/meter. The vehicles that were not running were unaffected. Of those that were running, eight showed no response to EMP, and 25 experienced minor nuisance failures, such as blinking dashboard lights. Three vehicles stalled when pulses exceeded 30,000 volts/meter.
The Commission noted that an EMP-induced failure of 10% or more of vehicles on a busy expressway could cause significant vehicle crashes, injuries, and deaths. Ten percent should be considered a conservative estimate, for today’s vehicles have far more electronic controls than the pre-2008 cars studied by the Commission.
EMP Protection for Vehicles
Carmakers include some EMP protection against surges caused by the starter motor and various electronic systems. Ideally, all vehicles should have full EMP protection to prevent massive accidents should an EMP attack occur. The complex electronics in modern electric vehicles might be more vulnerable than conventional cars.
Arthur Bradley, a NASA engineer who holds a doctorate in electrical engineering, is known for his online videos demonstrating Faraday shields. Bradley has developed the Transient Reducing Auxiliary Plug (or TRAP) surge protection device for vehicles. The TRAP plugs into a car’s cigarette lighter (Figure 
A), which is connected directly across the vehicle’s battery. An ultra-high-speed transient voltage suppressor inside the TRAP switches on within a few picoseconds of detecting an EMP and shunts the EMP pulse away from the vehicle’s battery cables.
A similar device called the TRAP-B is connected directly across the battery (Figure 
B).
An EMP pulse that reaches the battery cables is almost immediately shunted by the TRAP-B. Bradley also sells ferrite surge protectors that clamp around the cables (Figure 
C) to reduce the amplitude of a high-frequency EMP pulse.
You can learn more and watch a demonstration here. While Dr. Bradley cannot guarantee total EMP protection, his tests are encouraging.
A Higher Priority
If you’re away from home during an EMP attack, reliable transportation to your residence or prearranged security site will be your highest priority. If you’re at home or close by, making sure you have adequate water, food, and security may take precedence. In any case, a working car could be important if you can find fuel to run it. At minimum, the car’s battery can become a useful power source.
In “Life without Electricity,” a supplement to the 2008 EMP Commission report, Peter Vincent Pry described the rapid collapses in society that follow major natural disasters. He wrote: “Therefore, we can reasonably infer from the data on storm-induced blackouts and the known greater severity of high-altitude nuclear EMP that the consequences of an EMP attack on the United States’ infrastructures and society would be an unprecedented and first order catastrophe.”
If you’re intrigued, I’ve written more on surviving nuclear war and EMP for Mind Matters.
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