Can you explain me the following diagram Why cummulative frequency=1/year? What

Question

Can you explain me the following diagram

Why cummulative frequency=1/year?

What means1.E-07 or 1.E-01?

Why in logarithmic scale?

Please explain to me the following text in simple words

"A common way to describe societal risk is to calculate F/N curves. F/N curves illustrate the relationship between accident frequency and accident severity. On the abscissa the number of victims x (fatalities, injured people or both) is shown in logarithmic scale. On the ordinate the corresponding yearly frequencies F(x) for the occurrence of accidents with x victims are shown (also in logarithmic scale). For each given situation (population, traffic, DG traffic, route, weather, etc.) one F/N curve represents the societal risk. Figure gives an example for an F/N curve. "

1E+00 1.E-01 1.E-02 Current situation Total ban of DGs on A22 1.E-04 1E-06 1.E-07 1.E-08 1.E-09 10 100 Number of fatalities

Explanation / Answer

FN curves or FN diagrams gives us information about the societal risk.It depicts follwing three types of informations:

(a) Historical records of fatalities/risk/accidents.

(b) Result of Quantitative Risk Analysis(QRA)

(c) Criteria for analysing tolerability of the fatalities/risk/accidents

To under the diagram let us first understand how a societal risks may be presented as F-N curves. For this consider the results presented in Table

Rearranging the above table in decrasing order we get

To put this data in the form of plotting the FN curve, the frequency has to be expressed in terms of Cumltataive frequency as shown below

Event       Number of Fatalities     Frequency (f) per year    C.F

3                         120                      7.8x10-6                          7.8x10-6

2                          90                      6.21x10-6              13.0x10-6

1                          12                      74.8x10-6                          87x10-6

Now this CF is plotted against the no of fatalities to obtain FN curve.

(2) The unit of the CF data is in I/years because the data is obtained after adding the frequency of the fatalities to its previous value which is again the number of fatalities per year.

(3) Log scales are used to plot theF/N curves for the simple reason that the range of the values for f or N can span multiple orders of magnitude

(4)

Event Numer of Fatalites Frequency(f) per year 1 12 4 . 8 x 10 -6 2 90 6 . 21x10-6 3 120 7 . 8 x10-6

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