In the disastrous Lahaina fire on August 8, 2023, utility poles collapsed and electrical distribution wires broke and fell over roadways. In response, the local police chief stated: “If there was a downed power line that was live, we wanted to make sure that you didn’t go over a downed live power line.”1 Yet, both the local electrical utility2 and independent electric grid monitoring3 indicated that power lines in the area were, in fact, not energized. The consequence of the police action was that residents were trapped in their vehicles and found their choice to be “to jump into the ocean as well and be boiled alive by the flames or we would have just died from smoke inhalation and roasted in the car.”1
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This was not the first time that first responders had to cope with the issue of downed electrical distribution lines, and it certainly will not be the last. Thus, it is important that some appropriate advice be made available to authorities in charge of such incidents to minimize casualties.
It is unfortunate that fire service training in the real (or not real) hazards presented by electricity is minimal and often inadequate and incorrect. Recently, I published a comprehensive review of the hazards of electric shock from energized high-voltage power lines.4 The focus was on high-voltage wires in the air. Here, we need to consider the other scenario: downed power lines. Some of the basic research on this scenario was presented in my book Electrical Fires and Explosion.5
Electrical Power Distribution
First, here is a brief review of how electrical power is distributed in the United States. From the power-generating stations, electric power is sent out on the transmission network. This network runs at the highest voltages, which may be around 345 kV or even much higher. To service the users, this voltage needs to be stepped down, and this is typically done in two steps. First, the voltage is stepped down to the primary distribution voltage, which typically ranges from 7.2 kV to 20 kV. This voltage is still too high for nonindustrial users, so it gets stepped downed to the secondary distribution voltage, which is typically 120 V to 480 V.
The high voltage lines strung through a neighborhood are at the primary distribution voltage, meaning they carry 7.2 to 20 kV. It is also important to note that secondary distribution wires are generally covered with insulation, while primary distribution lines are bare—uninsulated. This is for economy and ease of servicing but taking safety aspects into account. Electrical wiring does not present a shock hazard if it is way out of reach, and primary distribution wiring is strung with sufficient clearances as prescribed by the National Electrical Safety Code6 or local public utility commission regulations.
Downed Conductors
In most cases, if an electrical utility conductor has fallen down, it is likely to be a primary distribution conductor and likely a bare conductor. There are, more specifically, three possibilities. The downed conductor can be (a) a phase conductor, meaning it is carrying the full line voltage; (b) a neutral conductor; or (c) a guy wire or messenger wire. The latter two types of conductors are not carrying any voltage; thus, there is intrinsically no electric shock hazard that can be associated with them.
So, what happens if a phase conductor breaks and falls across the roadway? The outcome will be strongly influenced by the terrain on which it falls.5 At one extreme, if it falls on wet soil, there is likely to be significant visible arcing and sparking. But furthermore, because a sizable current will flow under those conditions, this is likely to lead to an actionable electrical fault—a fuse or a recloser may open up and deenergize that circuit.
At the other extreme, the wire may fall on a concrete slab, which has a very high resistance to ground. In that case, the conductor may stay live and there may be no visible signs—i.e., no arcing or sparking.
In intermediate cases, the wire may fall on some terrain with modest resistance to ground, often due to a moderate amount of moisture being present. In such cases, there may be overt arcing and sparking, but this action will tend to dry out the contact area. Thus, visible signs may stop since the terrain has dried out locally, not because the circuit became deenergized.
Electric Shock
For there to be a danger of electric shock, it is not enough that a high voltage be present. There has to be the possibility of electric current to flow and to flow through the person, most notably through the chest area.7,8,9 And, for electrical current to flow, there has to be a complete path that includes a power source. Thus, it is well-known that birds can perch on a high-voltage wire with no harm. This is because the bird is contacting only a single conductor and cannot reach another conductor to complete a circuit path.
The same situation applies to people. Electric shock hazard only arises if things are configured so that there is a path for electrical current to flow through the person. If a person grabs a high-voltage conductor, whether he will be injured (or killed) then depends on his footwear. His shoes may be an electrical insulator, in which case current will not flow … but they also may not!
The Wire and the Motorist
Now, consider the crucial issue: What is the potential hazard to a motorist who would drive his car over the downed conductor that has not gotten deenergized? In extreme cases, a motorist may stop, get out of his vehicle, and grab the electrical conductor. This is, of course, outlandishly inastute behavior, but it has happened.10 With a basic modicum of common sense, the motorist will simply drive over the conductor and continue on his way. For this scenario, the hazard is nil.10
With this in mind, now consider prudent first responder policy. If there are no other exigencies, then of course the conventional first responder policy is to block off and prevent drivers from driving over downed conductors. This is highly conservative and does not take into account other risks and present dangers.
The Lahaina fire vividly demonstrated that such a policy across the board is likely to result in casualties—e.g., people may burn up in fire if their escape routes (which may require traveling over downed conductors) are blocked. The Lahaina fire was such an extreme casualty event that it bears repeating that, applied across the board, this is an unwise policy. Obviously, in hindsight, the police should not have blocked off (the very limited) escape routes available to the Lahaina residents on the basis that there were downed conductors (which, as stated above, were most likely not live) across the road.
While, as stated above, the risk is infinitesimally small for motorists driving over a live wire, the risk is exactly zero for driving over a deenergized conductor. Which is it? Generally, emergency situations are likely to be exigent; thus, it may not be feasible to enlist help from the local electrical utility. Instead, first responders can carry a simple tester to determine which it is. The Department of Homeland Security conducted a study11 on testing devices (“hot sticks”) intended for this purpose. Two devices were identified as suitable; they cost around $350 each, are small, and could be placed on any fire truck.
The Lahaina fire was an extreme life-loss incident. From what we know to this point, it appears that life loss might have been reduced, perhaps greatly reduced, had the first responders been knowledgeable about the hazards of downed wiring and taken appropriate action. This would have been to recognize the crucial need for rapid evacuation, understand that electric shock hazards are infinitesimal at worst and zero at best, and allow traffic to pass unimpeded. And, consistent with the science of electrical injury, there has never been a case incident where a motorist would have been injured by driving over a live high-voltage conductor, assuming that the motorist did not exit the vehicle.7
Endnotes
1. Boone, R., Hollingsworth, H., Lauer, C., Keller, C.L., “In deadly Maui fires, many had no warning and no way out. Those who dodged a barricade survived,” ABC News, August 23, 2023. bit.ly/3y81ZvU.
2. Pereira, I., Walsh, S., Cook, J., Harrison, J., “Maui Electric responds to lawsuit, claims power lines were de-energized after Aug. 8 fire,” ABC News, August 28, 2023. bit.ly/3Qmq0p9.
3. Marshall, B., Whisker Labs, Private Communication, September 14, 2023.
4. Babrauskas, V., “Water Streams, Power Lines, and Shock: How Serious a Hazard?” Fire Engineering, February 2019, pp.41-44. bit.ly/4a7pbHP.
5. Babrauskas, V., Electrical Fires and Explosions, Fire Science Publishers, New York, 2021.
6. 2023 National Electrical Safety Code (NESC), C2-2023, IEEE (2022).
7. Dalziel, C. F., “Electric Shock Hazard,” IEEE Spectrum Volume 9, Issue 2, February 1972, pp. 41-50.
8. Lee, R. C., Capelli-Schellpfeffer, M., and Kelley, K. M., eds., Electrical Injury: A Multidisciplinary Approach to Therapy, Prevention, and Rehabilitation, Vol. 720, Annals of the New York Academy of Sciences, New York, 1994.
9. Cadick, J., Capelli-Schellpfeffer, M., Neitzel, D. K., and Winfield, A., Electrical Safety Handbook, 4th ed., McGraw-Hill, New York (2012).
10. Mazer, W. M., Electrical Accident Investigation Handbook, 3 Vols., Electrodata, Inc., Glen Echo MD (var. dates).
11. Energized Wire Sensor, Department of Homeland Security, Science and Technology, 2019. bit.ly/4b2VJEn.
Vyto Babrauskas, Ph.D., is known for his research contributing to the field of fire investigation. He has published the books Ignition Handbook, Electrical Fires and Explosions, and Smoldering Fires. His firm, Fire Science and Technology Inc., is located in Cornville, Arizona.
