We hope that will come. The first step is to define and quantify an unacceptable loss of health. A reasonable starting point for such a marker is not death or long-term invalidity but, rather, an injury that has not healed after, say, three weeks. The loss of health is not spread randomly over all injury-causing events but corresponds to a rising degree of external violence. Therefore, the second step in the zero strategy is to identify and define the limit for external violence that generates an unacceptable loss of health.
Factors determining violence include vehicle and impact speed, and vehicle weight and configuration.
Similarly, the number of actual incidents that occur at different levels of violence is also relatively well known. A few examples might clarify how this works. This can be achieved by reducing vehicle speeds or separating unprotected road users and vehicles. With protected road users there are also opportunities to increase tolerance to violence, for example, by improving passive restraint systems or the vehicle's ability to absorb and deflect crash energy. Here the only option is, as with pedestrians, to reduce the violence-exposure equation by reducing the speed at impact or separating the two kinds of vehicles.