Table 4 Quantification of service using... | Emerald Publishing

Table 4

Quantification of service using the service indicators of state, reliability, availability and safety

Service indicator	Definition	Shown as	Equation/comment
State	The physical condition of the infrastructure	Weighted state of an asset by its extent per year	Based on deterioration when no preventive interventions are executed (Table 10) and on the weighted state after interventions when preventive interventions are executed (Table 11)
Reliability	The probability that an item can perform a required function under given conditions for a given time interval (NEN, 1999)	Reliability of each asset per year	Based on the probability of failure of each asset (Table 10) $R_{i}^{s} = 1 - P_{f- i}^{s}$ 10
Availability	The ability of a product to be in a state to perform a required function under given conditions at a given instant of time or over a given time interval assuming that the required external resources are provided (NEN, 1999)	Availability of each asset per year	Based on the interruption of traffic due to preventive (Table 11) and corrective (Table 12) interventions and the extent of each asset $A_{i}^{s} = \frac{365 - (t_{pr- i}^{prt} + t_{f- i})}{365}$ 11
Safety	Freedom from unacceptable risk of harm (NEN, 1999)	Probability of accidents to occur due to failures of an asset per year	Based on the probability of an accident to occur due to the failure of each asset (Table 10) ${Saf}_{i}^{s} = 1 - (P_{f- i}^{s} P_{a- i})$ 12

Service indicator	Definition	Shown as	Equation/comment
State	The physical condition of the infrastructure	Weighted state of an asset by its extent per year	Based on deterioration when no preventive interventions are executed (Table 10) and on the weighted state after interventions when preventive interventions are executed (Table 11)
Reliability	The probability that an item can perform a required function under given conditions for a given time interval (NEN, 1999)	Reliability of each asset per year	Based on the probability of failure of each asset (Table 10)10 $R_{i}^{s} = 1 - P_{f- i}^{s}$
Availability	The ability of a product to be in a state to perform a required function under given conditions at a given instant of time or over a given time interval assuming that the required external resources are provided (NEN, 1999)	Availability of each asset per year	Based on the interruption of traffic due to preventive (Table 11) and corrective (Table 12) interventions and the extent of each asset11 $A_{i}^{s} = \frac{365 - (t_{pr- i}^{prt} + t_{f- i})}{365}$
Safety	Freedom from unacceptable risk of harm (NEN, 1999)	Probability of accidents to occur due to failures of an asset per year	Based on the probability of an accident to occur due to the failure of each asset (Table 10)12 ${Saf}_{i}^{s} = 1 - (P_{f- i}^{s} P_{a- i})$