Mapping Accident Casualties Using Social and Economic Indicators

Geographic information for the home address of the accident casualty is obtained from the home-address post-code for each casualty. This allows the STATS 19 data base, the UK police system for reporting accidents, for the former Lothian Region in Scotland, 1990 to 1992, to be linked to social and economic indicators in the 1991 UK census and to the corresponding digitised boundaries at the smallest census geographical level (Output Areas, OAs) and post-code sector level in Scotland. For each post-code sector Standardised Casualty Ratio (SCR) which is commonly used in epidemiology to study rare diseases is calculated from the ratio of the number of casualties observed to that expected in the area. Adjusted SCRs are calculated, they are the ratios of the numbers of casualties predicted by social and economic factors that are measured at the census using Poisson regression to the expected numbers. Empirical Bayes Estimates (EMEs) are applied to prevent the results from areas with small populations being shown as too extreme. Results from the analysis indicate that accident risk to residents from deprived areas is high compared with those from affluent areas. Finally maps that can be used to identify areas in Lothian where there is relatively high SCRs are presented.