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Proximity detection systems Proximity detection systems for mine site vehicles There are intrinsic problems with all mine site vehicle drivers related to the reaction time of drivers to react urgently to a potential collision, writes T he problem of mine site vehicle collisions is closely related to general road accidents which in 2008, worldwide, claimed the lives of 1.2 million people, with 50 million injured at a cost of approximately US$3 trillion. Although this is mostly treated by authorities as a peculiarly human behavioural problem, the evidence would indicate that this is a technology problem and requires a technological solution, such as adaptive cruise control, vehicle location and separation in real time and automated vehicle proximity awareness. This article looks at a number of collision avoidance technologies to examine how they address the driver problem. Before we can address proximity detection systems for mine sites we should examine the causes of vehicle collisions at mine sites which come under broad headings: 1. Driver error The first thing to be aware of in apportioning blame to drivers for accidents is the fact that very few if any drivers get into a vehicle with the intent of injuring or killing themselves or anybody else for that matter. In many cases, the speed with which a person can respond – "reaction time" – is the key to assigning liability. It is common practice for accident reconstructionists simply to use a standard reaction time number, such as 1.5 seconds, when analysing a case. In fact, reaction time is a complicated behaviour and is affected by a large number of variables. There can be no single number that applies universally. Reaction time is a surprisingly complex topic. Unfortunately, most "experts" used canned numbers without a good appreciation for where the numbers originate, how they were obtained or the variables than affect them. Moreover, there are several distinct classes of reaction time, each with somewhat different properties. In this article, I briefly describe some keys issues. The discussion focuses primarily on driver reaction time. 2. Fatigue There is a need for a driver condition monitoring during early and late shifts to anticipate the response time of the haul truck driver. Measuring the driver's response time to detected objects, setting a limit for safe driving and warning the driver if they are getting close to this limit. If the driver goes outside these parameters the haul truck can report the situation to the controllers or shut down the haul truck until a supervisor can assess the situation. 3. Driver slow reaction times The seminal prior research is Henry and Rogers (1960) who performed experiments to test human reaction time to a constant stimulus. They compared reaction times to perform simple tasks, to reaction times to perform more complex tasks in order to determine whether or not the stress of complexity increased one's ability to react to the stimulus. The key was to keep the same test starting tasks and to keep the stimulus constant at all times. They made their subjects believe that all the tasks that they were about to perform would be important and that each would be timed. In actuality, the only interval of time Dr Patrick Gl ynn. 18 The Australasian Mine Safety Journal Spring 2011