Efficacy of System Warning

It can be observed that TTC thresholds between 1.0 and 2.6 s lead to a stronger reduction of accidents and injury levels as larger TTC thresholds. The simulation 

Study confirms the hypothesis stated above. Warnings towards a TTC threshold of 1.0 s or smaller evidently have only marginal effects. 

For the optimization of a system of active or integral safety, not only the positive effects, as given in Fig. 6.5, are important, but also the overall quality of the system and its components including false positives has to be considered. The number needed to 

In relation to avoided accidents, the number of warnings shows a stronger increase with increasing TTC thresholds. For decreasing TTC thresholds, the number of avoided accidents decreases more rapidly in relation to the number of warnings. 

Considering these numbers, the developer can decide whether the system quality is sufficient or not. The NNT is especially important if one considers the possible consequences of false-positive system actions. More false activations can lead to lower acceptance or in the worst case to the creation of new critical situations in traffic (see Sect. 2.2). If the consequences of a false-positive warning are assessed using appropriate experiments, a functional cost function can be constructed, giving the number of new accidents created by false-positive warnings and inappropriate subsequent reactions of the driver. (An appropriate quantification and the definition of such a function would suggest itself for further research.) 

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Efficacy of System Warning, Brake Assist, Automatic Braking ... 

Figures 6.5 and 6.6 give the results for system Warning with different thresholds for the earliest possible warning. The baseline consists of the 18 million situations as explained in Sect. 6.1. As the difference in the warning TTC was 0.2 s, each TTC threshold was simulated 100 million times in order to reduce fluctuations in the Monte-Carlo results to a magnitude well below the effect size. All ISS levels in this section have been computed using Option c (starting from ISS 16+) for the injury probability models (see Sect. 5.4.1). One would expect as hypothesis that the efficacy for low TTC thresholds converges to zero, as the driver needs a particular time to react, decide on an action, and act in response to a warning.

For a true-positive system action, both variants are different only in their efficacy. However, the consequences of a false-positive action are considered different regarding their severity A warning may eventually lead to a braking by the driver, but the intensity and duration of the braking is up to the driver. The driver s evaluation and decision loop additionally helps to avoid braking maneuvers as consequence of falsepositive warnings. A false-positive automatic braking lacks this second evaluation of the situation. 

Asgary A, Levy JK, Mehregan N (2007) Estimating willingness to pay for a hypothetical earthquake early warning systems. Environ Hazards 7(4) 312-320 Barker K, Santos JR (2010) Measuring the efficacy of inventory with a dynamic input-output model. Int J Prod Econ 126 130-143... 

Interactions. Involvement of protease inhibitors with the cytochrome P450 system provides scope for interaction with numerous substances. Agents that induce P450 enzymes (e.g. rifampicin, St John s wort) accelerate their metabolism, and reduce plasma concentration enzyme inhibitors (e.g. ketoconazole, cimetidine) raise their plasma concentration competition with other drugs for the cytochrome enzymes can lead to variable results. Ritonavir is itself a powerful inhibitor of CYP 3A4 and CYP 2D6. This effect is utilised when ritonavir in small quantity is combined (in capsules) with lopinavir to inhibit its metabolism and increase its therapeutic efficacy. The present account should be sufficient to warn the physician, and thereby the patient, to take particular heed when seeking to co-administer any drug a with protease inhibitor. 

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