EVALUATION OF THE EFFECTS
OF WEATHER CONDITIONS
ON THE TRANSPORT SYSTEM SAFETY
Woropay M., Bojar P.
Department of Machinery Operation, Faculty of Mechanical Engineering, University of Technology and Agriculture in Bydgoszcz, Bydgoszcz, Poland
Abstract: Safety is a priority criterion of the transport systems operation referred to as a total of means and activities connected with the movement of people and cargo. The paper identifies the source of safety threats of transport systems as a result of weather conditions on people and technical means of transport.
1. Introduction
Every year 40 thousand people are killed and about 1.7 million people get injured on the EU roads. Traffic accident data analyses are the starting point to improve the road safety. This is how traffic accident databases are created. The most extensive database is the European database CARE (Community database on Accidents on the Road in Europe) created in 1993. It contains 50 variables – accident information: number of accidents (also divided into urban areas), number and kind of car vehicles which participate in accidents, effects of accidents: number of persons killed and injured, division of victims according to age, sex, number of years of driving experience, etc.
The databases offer no data on detailed accident causes which in sociotechnical systems, such as road transport systems, can be created by the man located in the system, be a result of transport means operation or the effect of the operation of the environment. Figure 1 presents the accident causes in the Human – Technical Object – Environment system.
The basic source document of the accident recording system is the road traffic accident card filled in by police officers at the site of the accident according to their own evaluation of its course and accompanying circumstances.
The ‘human’ category includes all the people present in the system, namely: pedestrians, drivers and their passengers. The system environment is the cause of 35% road traffic accidents. Whether the vehicle was unfit for the job, being the cause of accidents, was considered by the police only in 2% of all the cases. One shall note that after the road traffic accident, no technical condition of the vehicle was evaluated due to the lack of diagnostic tools and no time available; the behavior of the driver, the road condition and weather conditions were the only ones evaluated.
1,9 35 87 2,5 39 94 2 36 93 0 20 40 60 80 100
Man Vehicle Road
[%
]
Road accidents Killed Injured
Fig. 1. Causes of accidents in the system <H-TO-E> [6]
The road traffic accident is a complex phenomenon and can result from both the human error, technical condition of the vehicle and the effect of the environment. Analyzing the causes of traffic accidents, one shall treat them as independent events which can occur both separately and together, see Table 1.
Table 1. Possible sequences of events which lead to a traffic accident
Item
Human Technicalobject (weather conditions)Environment
1 1 1 1 2 0 1 1 3 1 0 1 4 1 1 0 5 1 0 0 6 0 1 0
7 0 0 1
8 0 0 0
Table 1 shows the sequences of events which lead to transport system safety threat states, while: 1 – event where an element of the system affected the road traffic accident, 0 – occurrence where an element of the system had no effect on the traffic occurrence. System safety threat state no 8 is an abstract state which was not affected by any system element. The paper is an attempt to evaluate state no 7 in which the traffic accidents were affected by selected weather conditions being a form of the effect of the environment on the transport system safety.
2. Aim of the paper, research object and scope
The aim of the paper was to evaluate the effect of selected weather conditions on the safety of road transport systems which are the springboard for taking up actions which would enhance their safety.
The research covered both private and collective transport systems in the urban area up to 500 thousand residents to investigate the effect of selected weather conditions (clouds and rainfall) on the transport system safety.
3. Selected road traffic safety statistics
The road traffic safety (BRD) is a state which is the result of actions and economic, legal and engineering means which allow eliminating or restricting road traffic threats. The actions which are to enhance the road traffic safety start from recording data on accidents and other events for the purpose of the analyses [3].
Traffic accidents include those which have resulted in a loss of life or injury and collisions. A traffic accident is an event which takes place within the road area as a result of which at least one person was killed or injured. The collision is an event as a result of which only material losses were recorded [3].
The nature of keeping databases on the accident rate on the roads, both in respective countries and in the EU as a whole, is given in Table 2. The table contains data on the number of accidents (N.A.), number of vehicles participating in the events considered (N.V.), number of persons injured (N.I.) and the number of the dead (N.D.) as a result of traffic accidents.
Attempting the evaluation of the transport systems operation safety, one shall define the characteristics of each component of the system, that is the human, technical object, the environment, and to analyze their effect on the possibility of creating threats. The present study, bearing in mind the aim of the paper, gives only the identification and classification of the weather conditions types which can be the cause of threats. The following division was made: good weather conditions, dazzling sun, strong wind, cloudy, rainfall, snowfall, hail, fog, smoke.
Table 2. Selected research results of the accident rate in 15 EU countries [1] and in Poland [2]
N.A. N.V. N.I. N.D. UE-15 1215699 2262125 1643623 38406 Belgium 47444 86340 65294 1486 Denmark 7121 12430 8791 463 Germany 362054 708800 476413 6842 Greece 19671 33906 26336 1880 Spain 98433 173193 146917 5347 France 105470 182027 137426 7655 Ireland 6625 11192 9376 378 Italy 204615 395763 293358 6314 Luxemburg 769 1286 1100 62 Holland 33538 63138 40682 987 Austria 43423 76748 50164 931 Portugal 41642 68808 55662 1655 Finland 6196 10497 8156 415 Sweden 16947 29672 24747 560 Great Britain 221751 408325 299174 3431 Poland 51078 7548 63900 5640
5. Operational examinations
The aim of the present research is to provide information on the causes of threats being a result of weather conditions on the technical transport means and people present in the road transport systems as well as the information on the frequency of the occurrence of the weather conditions analyzed. Obtaining such data will make it possible to evaluate the degree of the correlation between: the number of road traffic accidents which took place in the analyzed weather conditions and the number of times these conditions occur a year. The research covers obtaining the following data:
number of accidents depending on the weather conditions,
number of persons killed as a result of accidents, depending on the weather conditions,
number of days when the analyzed weather conditions occur a year.
As it is seen in Fig. 2, the greatest number of traffic accidents and their victims are recorded in good weather conditions. It can be due to the fact that the percentage share of these conditions throughout the year is the greatest and due to an extensive sense of security of drivers driving in such conditions. Further research must be carried out in order to evaluate the effect of human activity and the technical object on the occurrence of road traffic accidents.
9 148 76 11 197 101 31 8 4 432 568 1 10 100 1000
Dazzling sun Good conditions Clody Rainfall and snowfall Weathe r conditions N um be r of r oa d ac ci de nt s
Road accidents Killed Injured
Fig. 2. Number of traffic accidents and their effects depending on the weather conditions in the urban area in 2004 [4].
192 140 116 34 0 50 100 150 200
Dazzling sun Good weather conditions
Cloudy Snowfall and rainfall Weather conditions N u m b er o f d ay s
Fig 3. Number of days of the weather conditions analyzed in 2004 [7].
Weather conditions are evaluated throughout the year. The measurement of cloudiness is made three times a day at. 7 a.m., 1p.m., 7p.m. The cloudiness is evaluated according to the 11-degree cloudiness scale (0-10); 0 – cloudless sky, 10 – totally cloudy sky. The paper applies the evaluation of weather conditions based on the daily cloudiness means, according to the road traffic accident card filled in by police officers on the spot:
(0-2) – dazzling sun,
(3-8) – good weather conditions, (9-10) – cloudy.
The precipitation is evaluated without dividing into rainfall and snowfall.
6. Methodology and selected results
Processing the data obtained involved determining the relationship between the number of traffic accidents and their effects under the weather conditions analyzed and the number of times such conditions occurred a year. To do so, the correlation of linear correlation coefficient was determined rxy, being a descriptive measure of the correlation between two
measurable characters. Determining the value of correlation coefficients of researched variables X and Y was verified with the significance test.
y x xy xy cov r , (1)
n
y
y
x
x
xy
cov
n 1 i i i
, (2)
n
x
x
n 1 i i
,n
y
y
n 1 i i
(3)
y x n 1 i i i xyn
y
y
x
x
r
, (4)
n
x
x
n 1 i 2 i x
,
n
y
y
n 1 i 2 i y
, (5) 2 n r 1 r t 2 . (6)where:
i x - value of variable X, i y - value of variable Y,x- arithmetic mean of variable X,
y- arithmetic mean of variable Y,
n
- number of observation pairs,x
- standard deviation of variable X,
y
- standard deviation of variable Y,
t- significance test for the correlation coefficient for the hypothesis made,
r
- correlation coefficient value,Table 3. Sample results of research required to determine the correlation between the number of days of good weather conditions and the number of persons killed under those conditions
x y
xi x
yi y
2 x xi
yi y
2
xi x
yi y
I 11 1 -5 -1.583 25 2.505889 7.915 II 11 0 -5 -2.583 25 6.671889 12.915 III 13 1 -3 -1.583 9 2.505889 4.749 IV 17 5 1 2.417 1 5.841889 2.417 V 22 5 6 2.417 36 5.841889 14.502VI 22 6 6 3.417 36 11.67589 20.502 VII 22 2 6 -0.583 36 0.339889 -3.498 VIII 22 4 6 1.417 36 2.007889 8.502 IX 17 2 1 -0.583 1 0.339889 -0.583 X 16 3 0 0.417 0 0.173889 0 XI 12 2 -4 -0.583 16 0.339889 2.332 XII 7 0 -9 -2.583 81 6.671889 23.247 x= 16 y = 2.58
x – number of days of good weather conditions,
y – number of traffic accidents in good weather conditions. 016
, 5
x
, y 1,934, rxy 0,798
Table 4. Values of the correlation coefficient of the values analyzed
Weather conditions
Number of accidents Dazzling sun
Good
conditions Cloudy Rainfall andsnowfall
Number of accidents 0.145 0.89* 0.79* -0.37
Number of the injured -0.054 0.85* 0.866* -0.439
Number of the dead 0 0.798* 0.456 0.354
Dazz ling sun Good cond ition s Clou dy Rain fall an d sn owfa ll Number of accidents Number of the injured
Number of the dead -0,6 -0,4 -0,2 0 0,2 0,4 0,6 0,8 1
Fig. 4. Graphic representation of the value of correlation coefficient of the values analyzed
Based on the sample results, a hypothesis was verified about no correlation between variables X and Y, namely the hypothesis H0: = 0, against an alternative hypothesis H1:
0
. The significance test for this hypothesis is given in the relation (6). Having carried out the significance test, it was shown that hypothesis H0 is true only for a part of the results obtained. However for two of the four weather conditions analyzed, there is a strong positive correlation between the number of times these conditions occur a year and the number of traffic accidents and their victims under the conditions analyzed.
7. Conclusions
The results allowed for an identification of weather conditions in which traffic accidents are most frequent and for defining the number of the injured as a result of the accidents. Based on the correlation coefficients determined and the significance test of these coefficients, it was shown that there is a strong positive correlation between:
Good weather conditions: number of accidents, number of the injured, number of
persons killed.
A big cloudiness: number of accidents, number of the injured.
Supplementing the databases on the road traffic accidents with the accident causes minus the effect of weather conditions, will indicate the scope of actions to be taken up to
enhance the road traffic safety. For example, future drivers taking up driving courses should be made aware of the fact that there are more accidents in good weather conditions than during rainfall or snowfall. An increased driver awareness of the threat causes will decrease the number of accidents and the number of the injured in those accidents as the greater the probability of recognizing threat causes, the easier it is to prevent the dangers [9].
References
1. http://europa.eu.int/comm/transport/care
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7. Techniczna Stacja Badawcza Mochełek k. Bydgoszcz, Wydziału Rolniczego Akademii Techniczno-Rolniczej w Bydgoszczy.
8. Greń J.: Statystyka matematyczna - modele i zadania. Państwowe Wydawnictwo Naukowe, Warszawa, 1978.
9. Smalko Z., Jaźwiński J.: Wybrana niekonwencjonalna metoda oceny niezawodności i bezpieczeństwa systemów technicznych w warunkach niepewności. Niekonwencjonalne metody oceny trwałości i niezawodności. XXXIV Zimowa Szkoła Niezawodności, Szczyrk, 2006.
