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An Analysis of Expressways Accidents in Singapore
Expressway data
As a digital map database of Singapore is not available the expressway profiles are obtained through GPS mapping. There are eight expressways in Singapore covering a total distance of 148km. These expressways provide uninterrupted high-speed travel (Max 90km/hr) for motorists with an average speed of around 50km/hr even during rush hours. Accident data This spreadsheet file included all the accident records for the years (1992, 1994, 1996, 1998 and 2000). The street ID in this tabular record is used to filter the accident records that occurred on expressways alone. This file included information such as the location where accident occurred in local grids, type of accident, type and severity of injuries, date and time of occurrence, type of road surface, the number of vehicles involved etc. The general expressway accident statistics account for nearly 25% of the total number of accidents. Moreover the number of accidents has doubled from the year 1992 to 2000 from 635 to 1380 respectively.  Fig. 1. Location of all crashes: Singapore Expressways in 2000 Data matching The accident data in local grid coordinates are converted to latitudes and longitudes, and exported as X, Y coordinates and overlaid on the expressway layer. One problem in accident analysis is the quality of data. The records are based on the police-reported accidents and these may be wrongly reported. However these can be easily seen on the GIS maps. Some modifications may be applied to correct wrong entries. An example of an accident distribution is shown in Figure 1. Methodology In this study, the analysis has not been confined to any particular class or type of accidents and rather towards utilizing the open nature of GIS in data manipulation. Hence it was decided to consider all the crashes initially and determine accident-prone locations by developing density maps. |