Dummies provide vital clues to what happens in a crash.

Hybrid III (frontal impact) and EuroSID II (side impact) dummies have experienced dozens of crashes first-hand. Their role is vital: the accident simulations rely on having a driver and passenger aboard to provide a full picture of likely injuries in a crash.

Hybrid III is designed to gather data from frontal impacts and EuroSID II gathers side-impact data, so the instrumentation in each is very different.

Our limb-by-limb anatomy guide explains how data is sourced.

The head is made of aluminum and covered in flesh-like rubber. Inside, three accelerometers are set at right angles, each providing data on the forces and accelerations to which the brain would be subjected in a crash.

The neck features measuring devices to detect the bending, shearing and tension forces on the neck as the head is thrown forwards and backwards during the impact.

Neither arm carries any instrumentation. In a crash test, the arms flail around in an uncontrolled way, and although serious injuries are uncommon, it is difficult to provide worthwhile protection against them.

Hybrid III's chest steel ribs are fitted with equipment that records deflection of the rib cage in the frontal impact. Injuries result if forces exerted on the chest, such as from the seat belt are too great.

The side-impact dummy, EuroSID II, has a different chest with three are instrumented to record compression of the chest and the velocity of this compression.

The abdomen in EuroSID II is equipped with sensors to record forces likely to cause abdominal injury.

EuroSID IIs pelvis has instruments fitted in its pelvic girdle. They record lateral forces that may result in fractures or hip-joint dislocation.

In Hybrid III, the upper leg area is made up of the pelvis, femur (thigh) and knee. Load cells in the femur provide data in frontal impacts on likely injury to all sections, including the hip joint which can suffer fractures and dislocations. A knee slider is used to measure forces transmitted through the dummy's knees, particularly if they strike the lower fascia.

Instruments fitted inside the dummies lower legs measure bending, shear, compression and tension, allowing injury risks to the tibia (shin-bone) and fibula (connecting knee to ankle) to be assessed.

Feet and ankle injury risk in the frontal impact is made by afterwards measuring distortion and rearward movement of the driver's footwell area.