CHAPTER 4 COMPARISON OF ACCIDENT RATE USING ACCIDENT RANKING

Transcription

1 6 CHAPTER 4 COMPARISON OF ACCIDENT RATE USING ACCIDENT RANKING 4. GENERAL To give an accident ranking among the three districts (Tiruchirappalii, Pudukottai and Thanjavur) and all the districts of Tamilnadu in India, accident rate is used. The purpose of this system is to take remedial measures to reduce accidents and compare the local rates with district rates, state rates and national rates. Ranking is done on the basis of the number of accidents and accident rates. The road safety level in Tamilnadu is taken considering four parameters, namely, accident severity index, accident fatality rate, accident fatality risk and accident risk. 4. INTRODUCTION Among different types of roads, the Highways (NH, SH, MDR, ODR - National Highways, State Highways, Major District Roads, Other District Roads) and roads in urban areas experience more accidents. Accidents do not occur uniformly on all days. Owing to environmental conditions and variations in traffic volume, accidents are innumerable on certain days. Accidents are mainly caused due to the improper interaction among various factors related to drivers, vehicles, roads and weather conditions. Large number of accidents occur at intersections in urban road networks. Higher number of accidents obviously indicate the presence of

2 6 more accident causative factors and higher accident proneness of that part of the road (Pignataro 97). For accident numbers, higher ranking is given to those sites with more accidents. The accident rate used for ranking is accidents per million vehicle kilometres. Accident rate provides a way of comparing local rates with district rates, state rates and national rates for similar road types. 4. RANKING LOCATION ACCORDING TO ACCIDENTS Except in some small places, resources will not permit the study of all locations. The locations (presented in Tables. and.) to be studied must therefore be selected. The next in doing this is to list or rank the locations according to accident experience (Pline 99). Ranking is done using two bases, namely, Number of accidents Accident rates. 4.. Number of Accidents The number of accidents is calculated in a simple way. Locations are ranked according to the number of accidents experienced at each location for the same period, usually a year. The one having the most accidents is listed first, the one with next most second, and so on. Locations having three or fewer accidents are omitted because they have too little experience to be significant. Lists (Tables 4. and 4.) in which locations are ranked according to number of accidents, can be prepared from a spot map by going through a location file, or if locations are numerous by computer. No manipulation of data other than counting is required before beginning the study. This simple

3 6 ranking by number of accidents is easy to explain. It is useful at a point when somebody urges signs or signals for safety at an unimportant location. This method is good to begin with and serves the purpose indefinitely in many jurisdictions. The number of accidents in sections of road has little significance unless all sections are of the same length. If sections are not of the same length accidents per kilometre, instead of number of accidents must be used. But ranking by number of accidents has disadvantages. For example, locations with few accidents at which inexpensive improvements could be very effective will be far down on the list and so may not be reached. Also, in extensive road networks, there may be many locations with nearly the same number of accidents. Then additional means are useful in choosing the best among the others. 4.. Accident Rate Rate or risk of accidents is the more useful method of ranking locations according to accident experience. A road location may have numerous accidents because it is much used rather than hazardous. Thus, the location having the most accidents is not necessarily the most dangerous to use. Conversely, lack of reported accidents for a specific period does not mean that there is no risk. Lists (Tables 4. and 4.4) in which locations are ranked according to accident rates. As risk or hazard may be expressed as an accident rate, it is the number of those experiencing accidents (involvements) at a location in a specified time divided by the number using the location in the same period. Because accidents are rare events, the simple rate is a very small decimal fraction. Therefore, for ease in writing, the rate is multiplied by a million and quoted as accident involvements per million users (Baerwald 976).

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12 7 Since the early 98s, the department of transport in UK has been developing, a national database of road network information. Another version called NIS (Network Information System) containing comprehensive record of accident details and traffic flows for the whole of the trunk road network was developed during 988. Using the NIS data base, In Yorkshire, Hayes (988) developed a system to identify and rank trunk road sites with clusters of accidents. Using the above system, the comprehensive record of accident details, traffic flows and road length for the three district road networks (Tiruchirappalli (city and district), Pudukottai and Thanjavur) and all the districts of Tamilnadu in India, ranking is assigned. The purpose of the above system is to inform those who are responsible for managing the road network and help them: To direct remedial action to the sites most in need of attention. To assess agent authorities proposals for remedial action within the context of regional priorities To assess the relative needs within the region. A system was first devised in 986 (the traffic section of the Yorkshire and Humberside regional office) based on accident record covering the preceding five year period. System was almost completed in 988. In this chapter, accident records cover the preceding four year period, (-6) as most of the road improvements were done previously. 4.4 DATA COLLECTION In this chapter data are collected from the records of police and highways departments during the period to 6 (area wise) and the statistical department from 997 to 8 (district wise) (CCRB and DCRB Tiruchirappalli, Pudukottai, Thanjavur). They are the number of accidents

13 7 (Fatal and Non fatal), traffic flow (ADT) in 8, the road length in km, area wise, district wise, state wise and nation wise. Clusters of accidents were picked out and the section of road within which they occurred determined. As an initial guide, all accidents in four years are included in the list of sites for ranking. In this way a list of 87 sites was compiled in three districts and all the 9 districts of Tamilnadu in India. 4. RANKING The first step in the ranking process is to obtain a detailed accident record for each of the sites identified. When the system of ranking was first devised, an attempt was made to weigh the feature of the accidents to highlight those sites which could be treated by engineering measures. However, weighing the features required an additional process and the results are not significantly different from those based on accident numbers alone. Therefore, the weighing stratagem was abandoned. 4.. Methodology Ranking is now done using two methods, number of accidents and accident rate. For number of accidents higher ranking is given to those sites with more accidents where there is a tie. There are two methods to be followed for ranking against number of accidents. a) In the first method, priority is given on the basis of accident severity starting with fatal and working through severe to slight in this method, considering the site one by one according to the ranking given to take remedial action against accidents. b) The second method is, by using rank correlation method, assigned the rank to the total number of accidents. Equal attention to the repeated rank for two or more number of sites is considered (Kadiyali 987).

14 Calculation of Accident Rate The accident rate used for ranking is accidents per million vehicle kilometres. Accident rates are normally considered better measures of risk than accident frequencies alone, since they account for differences in traffic flow. The standard equation for calculating accident rate for a location is found by dividing the accident experience by the exposure (Chand and Alex, Tuladhar and Justo 98). No.of Accidents (i.e.) Accident Rate (4.) Exposure where the exposure over a road way section is measured by the total vehicle kilometres of travel over the section for the period. (i.e.) Exposure = ADT 6 KM,, N per million vehicles km. (4.) where N is the number of years, ADT is the average daily traffic and KM is the length of the section (in km) No.of Accidents,, Accident Rate (4.) 6 ADT KM N In this chapter the length of the section is in km. The table ranked by accident rate provides a means of comparing the local rates with district, state and national rates for similar road types. 4.6 ACCIDENT ANALYSIS A number of studies on road safety have also been carried out in India, in different cities such as Delhi, Mumbai, Chennai, Ernakulam and Kolkata as well as on some highways. The notable studies include Srinivasan

15 7 and Prasad (979), Tuladhar and Justo (98), Kadiyali et al (98a), Valli and Sarkar (997), Victor and Vasudevan (998), Sikdar et al (999), Chand (999), Baviskar (999), Saija et al (), Sing and Misra (), Martin (), Chakraborty et al (), Chakraborty and Roy (). However, no significant studies have appeared on the accident characteristics of passenger vehicles in the districts of Tamilnadu. The rapid population growth and increasing economic activities have resulted in the tremendous growth of motor vehicles which is considered one of the primary factors responsible for increasing road accidents in many metropolitan cities of developing countries, including Tamilnadu, India. In this chapter an assessment of the current level of road safety in Tamilnadu is made utilizing data obtained from secondary sources. The road safety level in the state Tamilnadu is assessed considering four parameters, namely, accident severity index, accident fatality rate, accident fatality risk and accident risk Accident Severity Index The accident severity index measures the seriousness of an accident. It is defined as the number of persons killed per accidents. Table. presents the district wise accident severity index for Tamilnadu during the period 997 to 8. It is seen that the accident severity has gradually decreased in the districts Cuddalore, Dharmapuri, Kanniyakumari, Nagapattinam, Namakal, Theni, Thiruvarur, Thoothukkudi and Vellore, but has, since been increasing. It is observed that in there was a sudden rise of fatal accidents resulting in the increase of the accident severity index. Figure. represents graphically the accident severity index for the year 8 in terms of percentage. The figure shows that Kancheepuram has the highest percentage (%) of ASI in 8. The lowest percentage of % is in the districts of Chennai, Cuddalore, Nagapattinam, Thiruvarur.

16 76 Table 4. District Wise Accident Severity Index in Tamilnadu (Persons Killed per Accidents) Sl.No Name of The District Chennai Coimbatore Cuddalore Dharmapuri Dindigul Erode Kancheepuram Kanniyakumari Karur Madurai Nagapattinam Namakal Perambalur Pudukkottai Ramanathapuram Salem Sivagangai Thanjavur The Nilgiris Theni Thiruvallur Thiruvannamalai Thiruvarur Thoothukkudi Tiruchirappalli Tirunelveli Vellore Villupuram Virudhunagar

17 77 TIRUNELVELI TIRUCHIRAP P ALLI THOOTHUKKUDI THIRUVARUR % THIRUVANNAMALAI VILLUP URAM VELLORE VIRUDHUNAGAR CHENNAI % COIMBATORE CUDDALORE % DHARMAP URI DINDIGUL ERODE KANCHEEP URAM % KANNIYAKUMARI THIRUVALLUR THENI THE NILGIRIS THANJAVUR SIVAGANGAI SALEM RAMANATHAP URAM P UDUKKOTTAI KARUR MADURAI NAGAP ATTINAM % NAMAKAL P ERAMBALUR Figure 4. Accident Severity Index in the Year 8 (Persons Killed per Accidents) 4.6. Accident Fatality Rate The accident fatality rate is defined as the number of deaths per, vehicles. Table 4.6 presents district wise fatality rate in Tamilnadu during the period 997 to 8. There was a substantial decrease in fatality rate from 997 to 8. It may be noted here that although the number of accident deaths in Tamilnadu district wise did not decrease significantly. The vehicle population in the same period increased from,8,89 to,4,69 which resulted in a decrease of fatality rates of more than 6 per cent except the two districts namely the Nilgiris and Tiruvallur. Figure 4. is the graphical representation of the accident fatality rate for the year 8 in percentage.

18 78 Table 4.6 District Wise Accident Fatality Rates in Tamilnadu (Persons Killed per, Vehicles) Sl. No. Name of the District Chennai Coimbatore Cuddalore Dharmapuri Dindigul Erode Kancheepuram Kanniyakumari Karur Madurai Nagapattinam Namakal Perambalur Pudukkottai Ramanathapuram Salem Sivagangai Thanjavur The Nilgiris Theni Thiruvallur Thiruvannamalai Thiruvarur Thoothukkudi Tiruchirappalli Tirunelveli Vellore Villupuram Virudhunagar

19 79 VILLUPURAM % CHENNAI VIRUDHUNAGAR % % COIMBATORE % CUDDALORE DHARMAPURI DINDIGUL % TIRUCHIRAPPALLI THOOTHUKKUDI THIRUVARUR THIRUVANNAMALAI VELLORE TIRUNELVELI THIRUVALLUR % THENI THE NILGIRIS THANJAVUR SIVAGANGAI SALEM % ERODE KANCHEEPURAM KANNIYAKUMARI KARUR MADURAI NAGAPATTINAM NAMAKAL % PERAMBALUR 6% PUDUKKOTTAI RAMANATHAPURAM % Figure 4. Accident Fatality Rates in the Year 8 (Number of Deaths per, Vehicles) From the diagram, Villupuram district shows the highest percentage (%) of accident fatality rate in the year 8. But the lowest percentage of % occurs in Chennai district during the same year Accident Fatality Risk The accident fatality risk, defined as the number of accidental deaths per, population, shows an increasing trend in Tamilnadu district wise. From Table 4.7 it is seen that the fatality risk has increased marginally from 997 to 8 except in the districts Dharmapuri, Nagapattinam and Vellore. It showed an upward trend thereafter but was on the down again in when the number of deaths owing to accidents

20 8 Table 4.7 District Wise Accident Fatality Risk in Tamilnadu (Persons Killed per, Population) Sl.No Name of The District Chennai Coimbatore Cuddalore Dharmapuri Dindigul Erode Kancheepuram Kanniyakumari Karur Madurai Nagapattinam Namakal Perambalur Pudukkottai Ramanathapuram Salem Sivagangai Thanjavur The Nilgiris Theni Thiruvallur Thiruvannamalai Thiruvarur Thoothukkudi Tiruchirappalli Tirunelveli Vellore Villupuram Virudhunagar

21 8 THIRUVARUR % THIRUVANNAMALAI THIRUVALLUR % TIRUNELVELI TIRUCHIRAP PALLI THOOTHUKKUDI THENI THE NILGIRIS % THANJAVUR SIVAGANGAI VELLORE VILLUP URAM % SALEM RAMANATHAP URAM VIRUDHUNAGAR P UDUKKOTTAI CHENNAI COIMBATORE 6% NAMAKAL P ERAMBALUR MADURAI NAGAP ATTINAM % CUDDALORE DHARMAP URI % DINDIGUL KARUR % ERODE % KANCHEEP URAM 6% KANNIYAKUMARI Figure 4. Accident Fatality Risk in the Year 8 (Number of Deaths per, Populations) decreased compared with. Figure 4. is the graphical representation of district wise accident fatality risk in Tamilnadu for the year 8 in terms of percentage. The above diagram shows that Coimbatore and Kancheepuram have the highest percentage (6%) of accident fatality risk in 8. But the five districts of Dharmapuri, Nagapattinam, the Nilgiris, Thiruvallur and Thiruvarur have the least percentage (%).

22 Accident Risk Accident risk is defined as the number of accidents per, population. Table 4.8 presents the accident risk in Tamilnadu district wise for the same period 997 to 8. It is seen that accident risk increased from 997 to 8 but except the districts of Dharmapuri, the Nilgiris and Tiruchirappalli. The increasing trend of accident risk indicated that the chances of non-fatal accidents were gradually increasing, making the people of Tamilnadu district wise more vulnerable to the non-fatal type of accidents. Figure 4.4 is the graphical representation of the accident risk for the year 8. The highest percentage (7%) of accident risk is seen in Chennai district where as the Nilgiris shows the least (%) in the year 8. THIRUVARUR THIRUVANNAMALAI THIRUVALLUR % THE NILGIRIS % TIRUNELVELI TIRUCHIRAP P ALLI THOOTHUKKUDI THENI VILLUP URAM VIRUDHUNAGAR % VELLORE CHENNAI 7% COIMBATORE % CUDDALORE % DHARMAPURI % DINDIGUL ERODE KANCHEEP URAM KANNIYAKUMARI THANJ AVUR SIVAGANGAI SALEM RAMANATHAPURAM % P UDUKKOTTAI PERAMBALUR NAMAKAL KARUR MADURAI NAGAPATTINAM Figure 4.4 Accident Risk in the Year 8 (Number of Accidents per, Population)

23 8 Table 4.8 District Wise Accident Risk in Tamilnadu (Accidents per, Population) Sl. No. Name of the District Chennai Coimbatore Cuddalore Dharmapuri Dindigul Erode Kancheepuram Kanniyakumari Karur Madurai Nagapattinam Namakal Perambalur Pudukkottai Ramanathapuram Salem Sivagangai Thanjavur The Nilgiris Theni Thiruvallur Thiruvannamalai Thiruvarur Thoothukkudi Tiruchirappalli Tirunelveli Vellore Villupuram Virudhunagar

24 84 Figures 4. to 4. indicate the graphical comparisons of accident severity index, accident fatality rate and accident fatality risk of all the districts of Tamilnadu. Out of four parameters of road safety level in Tamilnadu district wise, three parameters namely accident severity index, accident fatality rate and accident fatality risk are taken to draw the trend chart for all the districts from 997 to 8. Since the value of the left out parameter is very high, the other three parameters are only considered. The values of the remaining parameters are very low compared to the fourth parameter and so the diagram is not so apt and visible. The fourth parameter for accident risk is shown separately. In Chennai district, there is a sudden growth in fatality risk and severity index from to 8. The same rise is observed in Coimbatore district from 4 to 8. A downward tend is seen in accident fatality rate in the districts of Cuddalore, Dharmapuri, Dindigul, Kancheepuram, Perambalur, Pudukkottai, Ramanathapuram, Sivagangai, Thanjavur, Thiruvarur, Vellore and Villupuram during the year 997 to. It is because the number of accident deaths did not decrease significantly during that period in the above mentioned districts. The vehicle population of those districts has increased which resulted in the % decrease of fatality rate. However this decreasing trend has reversed in. It showed a downward trend thereafter but was on the rise in 6. This is due to the increasing number of deaths compared to the year in some of the districts like Dharmapuri, Erode, Kanniyakumari, Madurai, Pudukkottai, Ramanathapuram, Tiuchirappalli, Thiruvallur, Thirunalveli and Vellore. Severity index, fatality rate and fatality risk based on road accidents show similar trend in the districts like Coimbatore, Dharmapuri, Kanniyakumari, Madurai, Nagapattinam, Ramanathapuram, the Nilgiris, Thiruvannamalai, Thoothukkudi, Vellore and Virudhunagar.

25 8 Figure 4.4 shows the graph of accident risk in the districts of Tamilnadu from 997 to 8. From the diagram, it is clear that vast variations of accident risk in the districts of Chennai, Coimbatore, Cuddalore, Dharmapuri, Dindigul, Erode, Kancheepuram, Kanniyakumari, Karur, Madurai, Namakal and Theni comparing to other districts. Regarding the vast variations, Chennai and Karur lead the other districts Figure 4. Severity Index, Fatality Rate and Fatality Risk of Road Accidents in Chennai

26 Figure 4.6 Severity Index, Fatality Rate and Fatality Risk of Road Accidents in Coimbatore Figure 4.7 Severity Index, Fatality Rate and Fatality Risk of Road Accidents in Cuddalore

27 Figure 4.8 Severity Index, Fatality Rate and Fatality Risk of Road Accidents in Dharmapuri Figure 4.9 Severity Index, Fatality Rate and Fatality Risk of Road Accidents in Dindigul

28 Figure 4. Severity Index, Fatality Rate and Fatality Risk of Road Accidents in Erode Figure 4. Severity Index, Fatality Rate and Fatality Risk of Road Accidents in Kancheepuram

29 Figure 4. Severity Index, Fatality Rate and Fatality Risk of Road Accidents in Kanniyakumari Figure 4. Severity Index, Fatality Rate and Fatality Risk of Road Accidents in Karur

30 Figure 4.4 Severity Index, Fatality Rate and Fatality Risk of Road Accidents in Madurai Figure 4. Severity Index, Fatality Rate and Fatality Risk of Road Accidents in Nagapattinam

31 Figure 4.6 Severity Index, Fatality Rate and Fatality Risk of Road Accidents in Namakal Figure 4.7 Severity Index, Fatality Rate and Fatality Risk of Road Accidents in Perambalur

32 9 4 4 Accident Severity index Figure 4.8 Severity Index, Fatality Rate and Fatality Risk of Road Accidents in Pudukkottai Figure 4.9 Severity Index, Fatality Rate and Fatality Risk of Road Accidents in Ramanathapuram

33 Figure 4. Severity Index, Fatality Rate and Fatality Risk of Road Accidents in Salem Figure 4. Severity Index, Fatality Rate and Fatality Risk of Road Accidents in Sivagangai

34 Figure 4. Severity Index, Fatality Rate and Fatality Risk of Road Accidents in Thanjavur Figure 4. Severity Index, Fatality Rate and Fatality Risk of Road Accidents in the Nilgiris

35 Figure 4.4 Severity Index, Fatality Rate and Fatality Risk of Road Accidents in Theni Figure 4. Severity Index, Fatality Rate and Fatality Risk of Road Accidents in Thiruvallur

36 Figure 4.6 Severity Index, Fatality Rate and Fatality Risk of Road Accidents in Thiruvannamalai Figure 4.7 Severity Index, Fatality Rate and Fatality Risk of Road Accidents in Thiruvarur

37 Figure 4.8 Severity Index, Fatality Rate and Fatality Risk of Road Accidents in Thoothukkudi Figure 4.9 Severity Index, Fatality Rate and Fatality Risk of Road Accidents in Tiruchirappalli

38 98 Accident fatlity rate Figure 4. Severity Index, Fatality Rate and Fatality Risk of Road Accidents in Tirunelveli 4 4 Accident fata.lity rate Figure 4. Severity Index, Fatality Rate and Fatality Risk of Road Accidents in Vellore

39 Figure 4. Severity Index, Fatality Rate and Fatality Risk of Road Accidents in Villupuram Figure 4. Severity Index, Fatality Rate and Fatality Risk of Road Accidents in Virudhunagar

40 ACCIDENT RISK

41 4.7 ADVANTAGES The tables together give a broad indication of the state of road safety on the roads in the region. It has been found that the ranking system serves other useful purposes, as mentioned below It acts as an early warning device in indicating locations where the accident record is deteriorating. It serves as a safety net in identifying sites which have not been detected by the other methods operated by the regional office. It gives a measure of the effectiveness of the remedial work carried out. 4.8 RESULTS A comparison of the four tables (Tables. to.4) shows that, although the rank of sites varied with method of ranking, the content of each table is remarkably consistent with approximately 9 percent of the sites in any one table also featuring in the other. The results of this work conformed to state and national trends in several ways; in particular there is a marked contrast between the frequency of accidents with urban areas and those in rural areas. Also motorways have much better accident records than all other roads. Krishnagiri district was started only in the year 4. So its data could not be found out for the previous years. Comparing local with district, state and national average, some sites identified and ranked have much higher accident rates. In both tables, some routes stood out as having a high incidence of accidents. The most prominent of these three districts for the first

42 accident rates, maximum number will be in Tiruchirappalli district. Of the sites identified for ranking, almost all were already under the subject of examination for remedial treatment, either by national improvement scheme or regional improvement scheme. 4.9 SUMMARY. A simple computerized system for the course ranking of accident sites has been developed to facilitate the management of the road network within the three districts namely Tiruchirappalli (city and district), Pudukottai and Thanjavur and all the districts of Tamilnadu in India. It is a two (accident rate and accident numbers) stage process of identification and ranking. Identification is carried out from the records of police, highways and statistical departments of Tamilnadu. Ranking and computing are being done on two bases, accident numbers and accident rate.. The correlation coefficient between the two methods of ranking in the three districts (87sites) is.44 and the correlation coefficient between the methods of ranks in all the districts of Tamilnadu in India is.6.. The accident risk showed an increasing trend from 997 to 8, but has since been decreasing. This again reiterates that the traffic management measures taken in the recent past have been effective. 4. In general, the accident severity index of Tamilnadu has shown an increasing trend, although there was a decrease in 7. Various traffic engineering measures undertaken in the

43 last few years might have helped in curbing the number of total accidents as well as fatal accidents.. A general decrease in accident fatality rates despite the considerable increase of motor vehicles, indicates that the traffic operation management in the state might have improved. 6. The rate of increase of the accident fatality risk was higher than the other parameters. This indicates that the safety improvement measures undertaken in the state have been effective. Method of ranking helps to take remedial measures against accidents. It is an early warning device in indicating the locations where the accident record is deteriorating. This feature allows a quick visual identification and ranking of the problematic location of area concerned. One of the main advantages of this system is that the authority can easily perceive and experience the economic loss incurred due to accidents and thus perhaps help to justify the allocation of funds needed for the countermeasures. Safety improvement measures like widening roads, constructing signals and flyovers, road markings and signage etc. to reduce accidents. For further improvement of reducing road accidents of all the 87 sites of Tiuchirappalli, Thanjavur and Pudukkottai, pavement marking is taken as one of the remedial measures, which is discussed in the next chapter.