The detailed statistic of accidents in UK demonstrates the type of vehicles involved, the casualties, and circumstances; it indicates a high level of the personal injury accidents. The risk graph presented in British Standard (2010 pp. 33-34) indicates the necessity of the risk reduction due to the high level of fatality/injuries represented by a letter C in the graph. It is possible to choose Cb, because the number of fatality in the UK is neither high nor low. According to the Reported Road Casualties in Great Britain 2010 report, there were “1,850 people killed that is 17 percent lower than in 2009 and 22,660 were injured, down 8 percent” (Department for Transport, 2011). The number of fatalities indicates a fall of 21 percent for car accidents, 19 percent for pedestrians, 15 percent for motorcyclists and a rise of pedal cycle fatalities by 7 percent.
The possibility of avoiding accidents represented by a letter P in the risk graph contains two types of the circumstances: possibility of avoiding under certain conditions and low level of possibility. Taking into consideration an operation of a process, rate of development of the hazardous event, ease of recognition of danger, avoidance of hazardous event and actual safety experience, it is possible to count the statistics of avoidance. The valuation of casualties is based on a consistent willingness to pay (WTP) approach, including the human costs, pain, grief, suffering, economic cost, medical cost, etc. The Reported Road Casualties in Great Britain 2010 indicates the total value of prevention of reported road accidents £15 billion in 2010 (Department for Transport, 2011). As the possibility of avoiding accidents includes all facilities provided in order to alert that the hazard can be avoided, a person can escape to a safe area and the time between the operator being alerted and event occurring exceeds 1 hour, it is possible to choose Pb in the risk graph.
Car usage in the UK represented by a letter F in the risk graph can be confirmed by the following statistic. Press release of Department for Transport indicates that “there are 33 million active vehicle records in the UK, and there are 44 million car tax reminders sent out per year” (2007). According to Guardian, the average cost of motor vehicles “for Britain’s 30 million drivers fell 5% or £123 in 2009 to £2,219 a year” and today “costs 18,49p a mile to run a new car compared with 19,5p in 2008” (Insley, 2009). Keating says that the citizens of the UK drive 19 miles a day (2007). As car dependency in the UK has increased since 1993, it is possible to choose F2.
A high number of early accidents represented by letter W3 in the risk graph can be confirmed by a total number of 208,648 of casualties reported to the police in 2010 (Department for Transport, 2011); this number is 6 percent, which is more than in 2009. In 2010, 9,700 reported casualties occurred when driving under alcoholic intoxication. A number of people died were 250 which are 14 percent of all road fatalities.
Safety integrity level (SIL) is used in order to indicate the level of necessity to reduce the risks of hazardous accidents. This index can be calculated by the division of the maximum frequency for the associated severity level by the total event. The numeric target value of this number can be used as the safety requirement specification jointly with the associated SIL. There are two tables of SIL (British Standard, 2010 p. 13): one for a high demand system where “frequency of demands for operation made on the safety function in no high than one per year” and another for a low demand system where demand is greater than one per year and continuous mode where demand is continuous. Besides, two ways of SIL determination can be used such as qualitative (risk graph method) and quantitative that is suitable for both high demand system and low demand system.
IEC 61508 as an international standard is used in industry and contains basic information of safety rules. This standard serves as a help measure to determinate the external risk reduction. Covering the complete safety life circle, IEC 61508 provides the information for three groups of phases within the industrial process such as address analysis, address realization and address operation. The International Standard can be considered as “a rapidly developing technology in mind; the framework is sufficiently robust and comprehensive to cater for future developments” (British Standard, 2010 p. 5). The main aspect of this Standard is “the conception of risk and safety function”.
Risk graph method helps determinate the safety integrity level analyzing the risk factors associated with the EUC control system. Such method is used in order to describe the nature of hazardous situations when the safety related systems fail or are not available (British Standard 2010 p. 22). Parameters choose for the particular graph serve together with the allocation to the safety functions. However, risk graph method does not consider the common caused failures of demand and layers of protection. According to the British Standard, this method is used in the process and offshore sector. Risk graph method is not appropriate in case when the confidence that residential risk is reduced to a specific quantitative value is needed.
British Standard 2010, Functional safety of electrical/electronic/programmable electronic safety related systems, BS EN 61508-5.
Department for Transport 2007, Press release 15: DVLA Beats Biggest Online Retailers.
Department for Transport 2011, Reported Road Casualties in Great Britain: 2010 Annual Report.
Insley, J 2009, ‘’, Guardian.co.uk.
Keating, M 2007, ‘’, Guardian.co.uk.