The Thoracic Trauma Index (TTI)

The Thoracic Trauma Index (TTI)

The Thoracic Trauma Index is used as a predictor of thoracic injury severity in the USSID dummy in standard American Side Impact tests.

The Index considers both rib and thorax acceleration in an impact.

The expression for calculating TTI is given by:

TTI = (G(R) + G(LS))/2

Where G(R) is the greater of the peak accelerations of either the upper or lower rib, expressed in g, and G(LS) is the peak acceleration in the lower spine (T12), expressed in g.

For the dummy to pass the test, the following conditions must be met:

(i) The TTI value must not exceed;
(a) 85g for a passenger car with 4 side doors, and for any multipurpose vehicle, truck or bus
(b) 90g for a passenger car with 2 side doors

(ii) The peak lateral acceleration of the pelvis shall not exceed 130g

(iii) Any side door, struck by the moving deformable barrier, shall not seperate totally from the car.

(iv) Any door not struck by the moving deformable barrier must meet the following requirements;
(a) The door chall not disengage from the latched position
(b) The latch shall not seperate from the striker
(c) The hinge components shall not separate from each other or from their attachment to the vehicle
(d) Neither the latch nor the hinge systems of the door shall pull out of their anchorage

For more information on the use and calculation of TTI, refer to the FMVSS 214 document