GIS as an aid to identify accidents patterns

GIS as an aid to identify accidents patterns


Alind Saxena, Ganesh Babu
Scientist(Environment & Road Traffic Safety, CRRI)
[email protected]

R. K. Bajpai
Head (Envirnoment & Road Traffic Safety, CRRI)

Dr. S. M. Sarin
Director (Road Safety) IRTE Retd. Scientist (Director -Grade) CRRI

The foundation of traffic safety work is information. The primary task is to establish a traffic accident database and than to maintain and analyse the same. The use of computers makes this effort more comprehensive and productive. Till now the data bases are in the form of linear record file system, nicely helpful in placing the analysed information only in tabular forms. For a better understanding and good decision-making visibility was not apparent in the databases and in it’s outcome. The GIS (Geographical Information System) a graphical information system that supports display and analysis of spatial data has revolutionised making and use of maps where as some times back it was a tedious exercise. The powerful aspect of GIS is its flexibility in modelling special objects to suit particular application requirement. It helps in understanding the characterstics of concerned area in aggregate by taking care of accident data and by linking to geographical features. Further accidents do not occur uniformly and their occurrence may be due to the number of limitations existing in those areas. These accidents could be studied and analysed to identify in some form of patterns through GIS. In this paper a conceptual effort has been made to identify the problem-zones. The complete zone under consideration can be an attention-requiring area or a subset of the same. To observe the patterns of accidents, it is necessary to mark the location of accidents in area on the map and thereafter, define the zones in terms of problems and resources. The analysed information would be useful in adopting improvement measures for finally selected zones.

Road accidents are one of the most important problems being faced by modern societies. The deaths of persons and serious economic loss caused by road accident demand a continuous attention in accordance with the spectacular growth in road transportation. The fact shows that India’s motor vehicle population is hardly 1 % of the world while its share in world road traffic accident is nearly 6%. About 61% accidents occur due to heavy vehicles in the country. The national highway accounts for 25% accidents, 34% of deaths and 28% of injuries on road. Likewise more and more statistics is available with different perspectives. The accident problem perceptions are mostly handled out to bring the conclusion based on data – primarily the FIR data from police departments. It requires consistency and accuracy in location reference and simultaneous consideration of FIR Data, Roadway Inventory Data and Work-zones. Analysis based on these different streams of data in-relation having impact and cause of dependency on each other parameters requires patience and skill. The different source makes the process complex though preference is for general, uniformed aggregate approach i.e. a macro level approach, which includes micro analysis as well. To deal with these limitations, to make the actions visible, to identify accidents patterns, GIS is a gateway to move ahead.

GIS Potentiality
GIS is Geographical Information System that supports the display and analysis of spatial data. GIS has its strength in providing capabilities to model the physical proximity of spatial features. The powerful aspect of GIS is the flexibility in modeling spatial objects to suit particular application requirement. GIS provide capability to store and maintain large data sets. GIS provides relational link between different streams of accident data – FIR Data, Inventory Data etc. It provides facilities to understand one to many, many to many and many to one relation-ship, which exists in spatial data. An expert may put his concentration on an intersection or a culvert or a type of accident or on a combination of parameters. The GIS provides new capabilities of data comparison and analysis that were not available in non-GIS linear reference system. GIS enables the safety experts to compare accidents along a road way segment with land use and zoning-data or population and other demographic data to gain a better understanding of the relationship of crash incidents or the zone-data could be integrated with accidents records to provide a true picture. Visual ability of GIS permits the mapping of FIR data, Inventory data and geometry data. Maps can be created to show the accidents of several targets groups (pedestrian, cyclist, intersection etc.) but also of various subgroups of victims or accident circumstances. The mapping provides beside a spot / intersection identification a way to establish zones and understanding of accident patterns. Patterns may cluster in linear or circular form or in other shapes.

The authorities are always on lookout to make roadways safer either by improving engineering measurements or by traffic monitoring. However, at times it is not advice able or feasible to implement safety improvement ideas in the whole city. The reason accidents do not occur uniformly, characteristics of roadways vary significantly. The reason may also be the geography of area, demography of area, funds allocation or combination of these. Safety improvement programs are required to be applied first in those areas (or zones) where the accident occurrence is high and land area is small. In this connection it is necessary to define zones.

What is Zoning?
The zoning process provides a systematic method for identifying accidents prone locations for safety improvement programs in cost-effective manner. Zoning identifies a subset of area having high number of accidents with respect to as little land area as possible. The motive is to gain maximum possible efficiency. The efficiency can be expressed as a ratio –

When the ratio is in form –> “ % of accident problem addressed >= % of land area covered” than zoning will yield a meaningful results.

The establishing of zones encourage safety programs where improvement measure can be incorporate where otherwise it is not feasible to apply safety improvement measures citywide. Zoning brings the following profits:

  • Efficient delivery of safety improvement programs where a majority of accident crashes or accident victims or economic loss exits.
  • Efficient use of funds in gray zones than it was applied to Whole City.

Though the zoning process is not new but GIS made it as an orderly process for selecting zones to gain the benefits from safety improvement programs and measures.