CÁPITULO VI: ESTUDIO DE COORDINACIÓN DE AISLAMIENTO
6.6 Calculo de Pararrayos en 10kV
6.6.2 Selección del equipo de protección
6.6.2.2 Pararrayos Línea Eléctrica 10kV
A substantial proportion of adult pedestrian fatalities in OECD countries are found to have been intoxicated with alcohol. Fontaine and Gourlet (1997) studied over 1,200 pedestrian fatalities in France in the 12 months to February 1991. About half had been tested for blood alcohol concentration levels (BAC), and they found that 35% of those tested had a BAC.0.8g/l. Fontaine and Gourlet reported that 90% of alcohol-impaired fatalities occurred at night, and that pedestrians were more likely than drivers to have been drinking. La Scala et al. (2000) reported USA data
indicating that in 1996 32% of pedestrian fatalities had a BAC.1.0g/l. Miles-Doan quoted 45% for Florida, and Holubowycz (1995) reported 38% for South Australia. One of the features that most strongly distinguishes older pedestrian fatalities, especially older women (Holubowycz, 1995; Fontaine and Gourlet, 1997) and the older old (Miles-Doan, 1996; O¨ stro¨m and Eriksson, 2001; see also Road Accidents Great Britain, 2000, Table 2g), is the much lower incidence of alcohol involvement. Nevertheless, the incidence is non-trivial. Fontaine and Gourlet (1997) reported that 11% of the over 65-year-old fatalities tested had a BAC.0.8g/l. Ha¨ndel (1981) mentioned debility arising from alcohol alongside physical and mental causes as one of four leading causes of older pedestrian accidents in Germany, and an earlier German study found alcohol to be frequently involved, even at low BAC levels (Bo¨hm, 1966; cited in OECD, 1970). Mori and Mizohata (1995) reported alcohol intoxication to be a feature of the at-risk older pedestrian in Japan. Holubowycz (1995) reported 15.8% of older male pedestrian fatalities with BAC>1g/l, although no older females. In the USA, Schiller et al. (1995) reported that 13% of all
admissions over 60 years old to an urban trauma centre were intoxicated with alcohol. Zegeer et al. (1994) reported that 15.4% of pedestrian injury accidents in North Carolina for 1980–90 involved drinking, including 3.2% of the over 75s. Zegeer et al. reported similar rates for national fatal accidents in the same period, 14.8% and 5.5%, respectively. National Highway Transport Safety Administration (NHTSA) data from the USA indicate that around 9–10% of pedestrian fatalities over 65 were intoxicated (NHTSA 1998, 1999, 2000). NHTSA (2001a) reported that the figure for those over 70 was 7% in 2000. Sjo¨gren et al. (1993) studied older traffic fatalities in northern Sweden (1977–86 data) and found that 15% of the older pedestrians who were dead on arrival at hospital had taken alcohol. Many of these had high BAC (>1.5g/l) and many had signs of liver disease, indicating a history of drinking. Data from the study by O¨ stro¨m and Eriksson (2001) of 286 fatalities in Umea, northern Sweden, between 1977 and 1995, have to be estimated from their chart (Figure 2, p175), but approximately 9% of all pedestrian fatalities 65–84 year olds tested positive for alcohol. UK data for the period 1985–1989 showed that about 26% of 70-year-old pedestrian fatalities for whom data were available had been drinking, with about 18% over 0.8g/l, and 2% over 3g/l (Everest, 1991). It is possible that the rates of alcohol involvement for older people are biased by under-reporting, as some studies have shown lower rates of alcohol testing for older
people than for, say, middle-aged men (e.g. Fontaine and Gourlet, 1995; O¨ stro¨m and Eriksson, 2001). Webb (1995) discusses this issue in detail. However, studies that test exhaustively have found similar rates. For example, the South Australian data were gathered in the context of mandatory testing of BAC for all injuries and fatalities. Rates for other age groups are highest at night and at weekends, and these are times when older pedestrians walk less frequently (Fontaine and Gourlet, 1997; O¨ stro¨m and Eriksson, 2001; Ward et al. 1994), which could partly explain the difference.
There is a good chance that older pedestrians will continue to have a relatively low incidence of alcohol involvement, but the picture could alter if social attitudes and patterns of activity change. There is evidence from European research that
successive cohorts of drivers preserve their driving patterns as they age (Hjorthol and Sagberg, 1998), and changes in drinking, such as increased drinking by younger adult women in recent cohorts, could also persist. There is some evidence linking intoxication rates to attitudes in different countries. Within the UK, rates are higher in Scotland and Wales than in England (Everest, 1991, 1985–89 data; Sabey and Staughton, 1980, 1978 data). O¨ stro¨m and Eriksson (2001) reported lower rates of intoxication among pedestrians in Sweden than studies from the USA and Australia. They attributed this to social and cultural differences, and to Swedish public policy, which inhibits the availability and consumption of alcohol. Studies in the UK have shown an increase in the alcohol involvement for younger adult women pedestrian accident victims over the past 25 years (Clayton and Colgan, 2001). The possibility that patterns of alcohol use by older people may change in the future cannot be ruled out.
Attitude changes are also believed to have affected behaviour in relation to drink- driving. Although there has been a recent decline in the number of drivers found with excess alcohol, rates of impairment among pedestrians have not declined so markedly. For example, between 1982 and 1992 in the USA, rates among drivers fell from 20% to 12%, whereas among pedestrians they fell from 39% only to 36% (IIHS, 1997; cited in La Scala, Gerber and Grunewald, 2000). Holubowycz (1995) reported a similar pattern in South Australia over roughly the same period. There have been extensive campaigns against drink-driving in many countries, but not in relation to walking. The campaigns against drink-driving appear to have succeeded, and several researchers have recommended similar efforts should be made in relation to walking. There are difficulties. Most agree that it would be impractical, for instance, to impose a legal limit on BAC for pedestrians. Although many states can detain intoxicated pedestrians, this is typically reserved for the obviously drunk, and risk appears to increase at relatively low BACs. Another difficulty is that for some drinkers, especially at night when public transport is limited, walking may be the safest transport available. Nevertheless, researchers have recommended raising public awareness of the risks of walking in the road environment after drinking (e.g. Miles-Doan, 1996; O¨ stro¨m and Eriksson, 2001).
Intoxicated pedestrians are not always at fault in accidents (O¨ stro¨m and Eriksson, 2001). Still, that is little comfort to the pedestrian, and there is evidence that alcohol affects mortality rates. Evans and Frick (1993) estimated that a BAC.1.0g/l
doubled the risk of death from a given impact for car occupants. Waller et al. (1997) found that, after allowing for the effects of crash severity as measured by the degree of vehicle crush, seat-belt usage, sex, and age, alcohol was associated with an increased risk of being admitted to hospital rather than being treated and released. This relationship was not present for those found to have taken other drugs, mainly cannabis. Miles-Doan (1996) studied pedestrian fatalities in Florida between 1988 and 1990, and found that alcohol increased the risk of fatality among pedestrians by about a factor of four, depending on the measure of intoxication used. Zajac and Ivan (in press) studied factors influencing injury severity for pedestrians crossing two-lane highways in rural Connecticut. They found that pedestrian alcohol use was one of the variables associated with more severe pedestrian injury. Bradbury (1991) reported that pedestrians under the influence of alcohol at an Edinburgh hospital had worse injuries and were more likely to have facial injuries than other injured
pedestrians. Given that older people are in any case more vulnerable to the consequences of an accident, this ought to be a concern.
In relation to older drivers and pedestrians, it is sometimes argued that alcohol is a negligible issue. However, some reviewers have taken a different view. For example, Planek (1981) suggested that the effect of alcohol at low levels is greater for older people, and discussed findings that, although overall rates of involvement are lower than for younger drivers, at higher alcohol levels older drivers have a greater risk of accidents. He cited the conclusion of a 1980 NHTSA report that ‘‘for drivers of 65 and over, alcohol is the most serious single contributing factor in fatal crashes’’ (p. 175). Zegeer et al. (1994) pointed out that quite small amounts of alcohol can interact with medications often taken by older people to produce large effects on performance. Because of older pedestrians’ existing functional problems, they argue that alcohol might present particular difficulties: ‘‘While not as great a problem for the older age groups, alcohol use nevertheless constitutes a serious pedestrian safety problem for which effective and immediate interventions are needed.’’ (p. 62). Because the rates of positive alcohol tests in older pedestrian accident victims are lower than those for younger adults, alcohol cannot explain why older pedestrians are at higher risk overall. Nevertheless, alcohol compromises the safety of any pedestrian, and a significant number of older pedestrian fatalities are over the legal limit for driving when they are killed. Those older pedestrians who do drink and walk increase their personal risk.
4.7
Summary
Certain situations are more commonly associated with accidents involving older people, and some groups of older people are more vulnerable than others in the road environment. Accident records include information about only some of the variables
that may affect older people’s risk. This means we cannot directly establish all relevant risk factors, and some of those we have described are therefore based on inference from general principles rather than casualty data. In addition, available measures of risk often incorporate only rough measures of exposure, such as
population size. The part played by illness and the effects of medicines in explaining older people’s risk as pedestrians, are discussed in section 3. The key points of this section are:
•
Older pedestrians tend to have accidents crossing the road in good weather and daylight, on weekdays, and near to home. For example, in one UK study, 73% were within 1km of home and 75% were on weekdays (Ward et al., 1994). There is evidence for increased risk at junctions and with reversing vehicles, but this may partly reflect the greater likelihood that an accident of a given severity will injure an older pedestrian and so be reported. One study in the USA found that about 22% of both fatal and all injury accidents to 45–64-year-old pedestrians occurred at junctions, but for people aged 75 years or over, 27% of all injury accidents and 35% of fatalities were at junctions (Zegeer et al., 1994).•
Among the normally ageing, the older old have a substantially elevated accident risk and slow walkers are likely to be vulnerable. A study in New Zealand concluded that the risk of experiencing a collision of a given severity was five times greater for those over 79 compared to 25–69 year olds (Keall, 1995).•
Men have a higher risk per capita of pedestrian fatality at most ages, although the gap between men and women may attenuate among the younger old. For example, 1993 UK data showed that the rate of pedestrian fatalitiesper 100,000 people was 1.58 times greater for men compared to women aged 70–79 years (estimated from Broughton, 1997, Figure 2.6). South Australian data from the 1980s illustrate a narrowing of the gap between men and women: for the three age groups from 56–65, 66–75, and 76–84, the ratios were 4.1, 0.9, and 1.5, respectively. The relative risk varies between countries as well as between precise age groups. Women appear to be at higher risk of injury from falls, even from late middle-age. By some measures of exposure, women have been found to have a higher accident risk in some age groups. An understanding of the reasons for sex differences is limited.•
There are reasons to think that older people who have recently given up driving are at higher risk, in part because they are likely to belong to other high-risk groups. For example, they may have stopped driving because of poor vision.•
Alcohol is associated with accident risk for pedestrians. Older pedestrians are less likely to have been drinking than younger adult pedestrians, and the evidence suggests that, at present, among older people this problem is largely confined to younger old men. In France, 9% of all older pedestrian fatalities tested had blood alcohol concentrations over 0.8g/l (Fontaine and Gourlet, 1997).4.8
Research implications
European research on older drivers has in recent years shifted focus towards studying specific groups, rather than attempting to treat older people as a
homogenous category (Hakamies-Blomqvist and Peters, 2000). Pedestrian research could develop fruitfully along similar lines.
We have been able to make direct links to accident or injury risk only when a factor is routinely recorded (e.g. age or sex) or epidemiological studies have been done. Specific research would be useful to establish whether, for example, slow walkers and former drivers do have measurably greater risk. As indicated in the introduction, the measurement of risk depends on using appropriate measures of exposure, and studies would need to take that into account. The investigations by Fontaine and Gourlet (1995) and Keall (1995) provide good examples of appropriate research methods.
Other factors, such as socio-economic status, are sometimes mentioned in relation to accident risk, but there have not been sufficient data to justify a conclusion. For example, pedestrians from lower income groups appear to be at higher risk, but there are few data specifically on older people, and differences may be explained by collinear variables such as the different road layout of urban and suburban
residential areas. Understanding the effects of road layout and road situations on accident risk, particularly the apparent increase in risk for older people at junctions and from reversing vehicles, is itself an important area for continuing investigation. These would be interesting topics for new research.
Beyond establishing the characteristics of high-risk older people, there is
speculation but little clear understanding of the mechanisms by which particular factors increase risk, except perhaps in simple cases like alcohol impairment. Because some of the factors are not as readily modified as, say, alcohol
consumption, understanding these mechanisms may be necessary to understand how the most effective intervention might be made.