Page 131 - 360.revista de Alta Velocidad - Nº 5

Probabilistic Safety Analysis of High Speed and Conventional Railway Lines

Note that in Table 4 the frequencies and severity levels of consequences are classified as levels
1 to 7 and 1 to 4, respectively.
Note that both, frequencies and consequences are quantified in levels related by a factor of 5.
In addition, to assign numerical risks of each frequency-consequence combination, instead of
multiplying the two row and column entries, they add the levels (exponents of power 5), on the
basis that the power product of the same basis is another power with the same basis and the
sum of the exponents. In other words, the indices contained within each of the central cells,
which take integer values between 2 and 11, are the sum of the levels of their row and column.

Table 4 with the entries multiplied by a factor, which depends on the particular event being
analyzed, and two threshold values allows classifying the individual risk, measured in probability
of fatality per year, into three regions (see Table 5): the region where risk must be removed,
the region where the risk must be mandatory analyzed in detail and the region where no further
action is required. One example is Table 5, where the event refers to an accident of a commuter
assuming 500 journeys per year and 10E+06 passenger journeys per year. This means that the
cell in Table 4, with Frequency 7 and consequence 1, that is, a risk level of 0.25 fatalities per
year corresponds:

Which is the value in the same cell of Table 5

Table 5 Table for risk assessment recommended in the document published by the RSSB (Railway
Safety Standards Board).

International Congress on High-speed Rail: Technologies and Long Term Impacts - Ciudad Real (Spain) - 25th anniversary Madrid-Sevilla corridor 129