Call for TMA against Truck Terror

Heavy truck with rear mounted energy dissipating barrier.
Truck Mounted Attenuator, TMA. on a heavy truck with brakes applied on all wheels. TMA is required in Sweden at temporary road works to protect both road users and workers. Therefore, numerous TMA vehicles are available for hire and may be used to protect crowds against sick or evil drivers. Estimates indicate that a 24000 kg truck like this could have stopped the 12000 kg truck used in Stockholm on April 7 within a braking distance of less than 10 meters.

The April 7 terror attack in Stockholm became more dangerous due to roadblockers in the Drottninggatan street. A strike by a 12000kg truck at 70km/h may eject an unrestrained 1000kg concrete block at 100km/h.

Well anchored stationary devices may stop the truck chassis, but if the barrier is too stiff, truck parts will become separate projectiles threatening people downstreams, like in the video below.

Seemingly unaware of Newton’s laws of motion, German researchers carried out full scale crash tests with a truck colliding with concrete blocks. Not surprisingly they found that “the anti-terrorist barriers were pushed like billiard balls” (quote with video, Daily Express Apr 12, 2017).

If such a “billiard ball” with a mass of 1000 kilograms is hit centrally by a 12000 kilogram truck at 70 kilometers per hour, simplified calculations indicate that it may be pushed away with a speed between 65 and 130 kilometers per hour.

The truck speed will be reduced to 65 km/h after an inelastic impact (the truck and the concrete block move together) and to 59 km/h after a fully elastic impact (increasing the block speed to 130 km/h).

Ground friction forces and vehicle lifting effects will reduce the speeds.

This blog post was hastily prepared after my discovery on April 29 of the international unawareness of Newtonian mechanics.

I will therefore post more info quite soon and give you access to a downloadable Excel sheet, containing the formulas for my calculations. There are also more video links available, demonstrating retractable net barriers etc.

Until I have prepared a specific opt-in page, you may subscribe to the Bildrullen blog posts in general to be notified. The subscription form is in the right hand column for desktops and in the bottom menu for mobiles.

Regards
Lennart S

Författare: Lennart Strandberg

Professor (emeritus) vid Linköpings universitet; Oberoende haveriutredare och olycksanalytiker i eget företag stop.se; Körkort A BE CE DE; Tävlingsförare i svenska bileliten och på mc i enduro; Experimentell och epidemiologisk forskning om trafikantbeteende, biomekanik och kördynamik i kritiska situationer; Professor i teknisk olycksfallsforskning vid tidigare Arbetsmedicinska institutet.

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