Efficacy of System Automatic Braking

There are three different approaches to interpreting the surface First, holding deceleration constant, an increase in TTC threshold leads to increasing avoidance. One possible reason is that the earlier the braking TTC, the more time the pedestrian has for escaping the vehicle path and thus resulting in accident avoidance. Another is that the vehicle has more time to brake. However, the accident avoidance is nonlinear (saturation) increases in TTC thresholds do not always imply earlier triggering, since additional conditions such as pedestrian trajectory (with respect to probability of collision) need to be satisfied. 

Second, examining lines of constant TTC threshold indicates that maximum braking deceleration has a quite linear effect on accident or injury avoidance. 

the contour lines of the surface represent contours of equal efficacy. The gradient to the contours gives indications on the relationship between TTC and deceleration. The gradient at high decelerations is in direction of TTC thresholds at lower decelerations, the gradient is in direction of both TTC thresholds and decelerations. 

The relationship is thus not a linear one. At high deceleration, changes in TTC threshold dominate. At lower decelerations, changes in TTC threshold and changes in deceleration are both important. Following a line of equal efficacy, increased TTC thresholds do not lead to linearly decreased levels of deceleration but accelerated 

20 Number needed to treat for avoided accidents for system Automatic braking  

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