If the bucket bomb which apparently failed to detonate today in the London underground train had exploded successfully at Piccadilly Circus there would have been many casualties. In this short study, we will simulate such an explosion for educational purposes informing the public and the authorities about the effects.

According to the News, an improvised bomb placed in a bucket and left on the floor of an underground carriage in London caused injuries and damages in the London underground train. We don’t know yet whether it was an IED (i.e. an improvised explosive device meant to destroy and kill by its blast wave and shrapnel or if it was an incendiary bomb whose lethal effects are mostly burns and asphyxiation.
The Arms Control Center provides an approximate assessment of the effects such an IED may cause so that the authorities in London can take appropriate measures in case another such a bomb is found. At the same time the emergency personnel, the first responders, and the general population will get an idea of the destructive effects of such a device so that they can evacuate the possible ground zero at reasonably large distances without exaggerations and panic which would disrupt the social and economic life of London

According to a short video which is now all over the internet, the improvised bomb, we don’t call it an improvised explosive device yet, was inside a bucket half covered by a plastic bag apparently used to carry the bomb to ground zero, which was on the floor of an underground carriage. The same video shows that the device is on fire before its explosion while investigators have recovered what appears to be a circuit board from the scene where the device was placed. Apparently, the bomb was either attached to a timer or it was meant to explode by remote control. Judging from the damages caused in the carriage and the injuries sustained by the passengers the device must have finally acted more like an incendiary bomb, failing to initiate a detonation, although it is still unclear whether it was an IED that is an improvised explosive device meant to kill by a blast wave and shrapnel or it was actually meant to be an incendiary bomb such as the one found in the Athens Metro in 2012. In any case, the Arms Control Center assumes a conservative scenario according to which the device was indeed an IED and that the volume of a sizeable bucket allows for an IED of roughly 50 lb of TNT. We will use this conservative representation for a bucket bomb to estimate the damage such an IED would have caused had it exploded in the open at the center of the Piccadilly Circus. Please note that the damages and injuries caused by a bucket bomb explosion inside the underground carriage would have been much more severe as the walls of the closed carriage would have acted as a tamper enhancing the effects of the blast wave and the shrapnel. Our software, the First Responder Support Tools displays the mandatory evacuation distance and the shelter-in-place distance which are respectively, XXX and XXX feet.

Once detected, a pipe bomb should not be dismantled or even approached as any mistake could trigger an explosion. Since dismantling the pipe bomb is virtually forbidden, the typical method of disarming such a bomb is to destroy it in place or relocate it to a remote area where it can be safely destroyed by experienced bomb disposal personnel. Only authorized law enforcement and bomb disposal personnel should be allowed to approach and handle the explosive device.
Once a bucket bomb is located, all people should assume a safety distance from the bomb until authorized bomb disposal personnel disarms or destroys or relocates the bomb to a safe area. We call that distance, Minimum Evacuation Distance and we define it as the range at which a life-threatening injury from blast or fragmentation hazards is unlikely. However, even at such distances, non-life-threatening injuries may occur.

Let’s now define the Minimum Evacuation Distances associated with a bucket bomb modeled in our case as a 50 lb IED.

The US Department of Homeland Security classifies Minimum Evacuation Distances into two major categories
Building Evacuation Distance which for a 50lb IED is 150 feet (roughly 45 meters)
Outdoor Evacuation Distance which for a 50lb IED is 1850 feet (roughly 560 meters)
Building Evacuation Distances apply to people who are inside buildings while Outdoor Evacuation Distances apply to people who are outdoors, in the streets or in an open field.
Another interpretation of these distances is that a building evacuation distance is actually a mandatory evacuation distance while an outdoors evacuation distance is a shelter-in-place distance.
People inside buildings which shield them from a bucket bomb are provided with a high degree of protection from death or serious injury in case of a bucket bomb explosion; For such people, we apply Building Evacuation Distances evacuating them to a distance of 150 feet (roughly 45 meters) away from the bucket bomb. However, glass breakage and building debris may still cause some injuries, therefore whenever a bucket bomb is found in a building it is advisable to evacuate the entire building floor and at least the adjacent ones.
On the other hand, if there are people who are in the vicinity of a bucket bomb and cannot enter a building to seek shelter they should be evacuated to the Outdoor Evacuation Distance, which is 1850 feet (roughly 560 meters) away from the bucket bomb. If evacuation is impossible all people inside the outdoor evacuation distance should at least shelter in place.
As an exercise, we will assume that a bucket bomb explodes at the center of the Piccadilly Circus. We located on the satellite map the ground zero of the explosion and our software plots two overlapping concentric circular areas centered on ground zero. The yellow circular area has a radius equal to the Outdoor Evacuation Distance that is 1850 feet (roughly 560 meters), while the red circular area which is of a radius of 150 feet (roughly 45 meters) is the mandatory evacuation distance.
At first sight, the Outdoor Evacuation Distance for a 50lb IED defined by the Department of Homeland Security seems unrealistically large. If such a bucket bomb had been found at the Piccadilly Circus, according to the proposed Outdoor Evacuation Distances many London City blocks should have been evacuated, causing unnecessarily many exaggerated financial and psychological impacts. Although the much more realistic 100-meter red color Evacuation area would suffice for bucket bombs, our Arms Control Center advises that the DHS standards should be applied in all cases, if possible.
To further analyze the effects of a bucket bomb, modeled in our case as a 50lb IED, we apply our software (First) to estimate additional risk zones.
For example, the turquoise circular zone which has a radius of 250 feet (roughly 76 meters) indicates the threshold for minor glass cuts meaning that people outside that zone are not expected to sustain any risks from glass fracture, let alone from the blast wave or other bomb effects.
On the other hand, the pink circular which has a radius of 105 feet (roughly 32 meters) indicates the threshold for mild injuries due to blast and fragments.
Finally, the inner zone which has a radius of 70 feet (roughly 21 meters) represents the lethality threshold so that all people inside that central zone may sustain lethal injuries.

Disclaimer: This is just a short tutorial assuming that a bucket bomb is equivalent to a 50 lb IED regarding its risk zones and evacuation distances. The Arms Control Center advises you to follow only the instructions of your governmental authorities in case a bucket bomb is found. We will not be responsible for decisions you made or you did not make because of this tutorial!

Comments are closed.