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system. Important process details include: capacity, utilization of capacity, marginal
cost of use, capital and maintenance cost, reliability, vulnerability-to, and resilienceto, along with the details of the couplings between network layers.
Capacity is the maximum rate at which goods and services could be produced,
consumed, or transported using the infrastructure. For instance, a power transmission line may have a capacity of 100 kW, and a canal might have a capacity of
1 million gallons/h.
Utilization is the percentage, fraction, or simple rate at which the infrastructure
is employed to produce, consume, or transport goods and services. Utilization cannot exceed 100% of the capacity. Infrastructures often experience chaotic failures
when utilization approaches capacity, because the stress involved in near-capacity
operations tends to trigger many unpredictable problems. Power grids are known to
become unreliable when utilization exceeds 85–90% of capacity, so power grid
regulations in the USA typically require operation below 85% of capacity.
Marginal cost to use the capacity is the cost of processing the next unit of a good
or service using the infrastructure, not including capital and maintenance cost. For
instance, a thousand gallons of potable water in the USA costs roughly 1 dollar
(2018 USD). This marginal cost might include maintenance, operational, and energy
costs, but does not include the capital cost or finance charges required to build the
infrastructure. Water customers in the USA typically pay close to the marginal cost
for water, whereas capital costs and water prices are heavily subsidized.
Capital cost is the cost to build an infrastructure, not including maintenance and
operational costs. Capital costs tend to be large, and in many cases are heavily subsidized using publicly funded grants and low-cost loans.
Reliability is the percentage or fraction of the time that an infrastructure is adequately functioning. Actual reliability and designed (predicted) reliability are two
different concepts. Often the actual reliability is lower than the designed (predicted)
reliability). Most infrastructures in the USA are designed to keep reliability well
above 99% after considering all known hazards such as earthquakes, storms, heat
waves, floods, and accidents. Reliability is a common form of regulatory quality
requirement imposed on infrastructure operators by their governors. Reliability is a
measure of safety and quality for infrastructure.
Vulnerability-to some hazard is the degree of damage, downtime, cost, degradation, or loss of life that will occur if a specific magnitude and duration of hazard
occurs against a specific infrastructure. The longer and more severe the hazard, and
the weaker the infrastructure’s design standards, the more vulnerable the infrastructure is to the hazard.
Resilience-to some hazard is the infrastructure’s capacity to quickly and efficiently adapt to and recover from a damaging event. Resilience usually involves
change, because if a failure occurred in the system, the system often needs to be
redesigned. Resilience of hard infrastructure is aided by its redundancy, diversity,
(in)vulnerability, and by the effectiveness of the governing soft infrastructures.
Couplings between layers are points of contact between different types of
infrastructure—like where the power grid runs water pumps, or where a utility’s
staff act to maintain or restore a water pump. These couplings are key functional
B. L. Ruddell et al.
system. Important process details include: capacity, utilization of capacity, marginal
cost of use, capital and maintenance cost, reliability, vulnerability-to, and resilienceto, along with the details of the couplings between network layers.
Capacity is the maximum rate at which goods and services could be produced,
consumed, or transported using the infrastructure. For instance, a power transmission line may have a capacity of 100 kW, and a canal might have a capacity of
1 million gallons/h.
Utilization is the percentage, fraction, or simple rate at which the infrastructure
is employed to produce, consume, or transport goods and services. Utilization cannot exceed 100% of the capacity. Infrastructures often experience chaotic failures
when utilization approaches capacity, because the stress involved in near-capacity
operations tends to trigger many unpredictable problems. Power grids are known to
become unreliable when utilization exceeds 85–90% of capacity, so power grid
regulations in the USA typically require operation below 85% of capacity.
Marginal cost to use the capacity is the cost of processing the next unit of a good
or service using the infrastructure, not including capital and maintenance cost. For
instance, a thousand gallons of potable water in the USA costs roughly 1 dollar
(2018 USD). This marginal cost might include maintenance, operational, and energy
costs, but does not include the capital cost or finance charges required to build the
infrastructure. Water customers in the USA typically pay close to the marginal cost
for water, whereas capital costs and water prices are heavily subsidized.
Capital cost is the cost to build an infrastructure, not including maintenance and
operational costs. Capital costs tend to be large, and in many cases are heavily subsidized using publicly funded grants and low-cost loans.
Reliability is the percentage or fraction of the time that an infrastructure is adequately functioning. Actual reliability and designed (predicted) reliability are two
different concepts. Often the actual reliability is lower than the designed (predicted)
reliability). Most infrastructures in the USA are designed to keep reliability well
above 99% after considering all known hazards such as earthquakes, storms, heat
waves, floods, and accidents. Reliability is a common form of regulatory quality
requirement imposed on infrastructure operators by their governors. Reliability is a
measure of safety and quality for infrastructure.
Vulnerability-to some hazard is the degree of damage, downtime, cost, degradation, or loss of life that will occur if a specific magnitude and duration of hazard
occurs against a specific infrastructure. The longer and more severe the hazard, and
the weaker the infrastructure’s design standards, the more vulnerable the infrastructure is to the hazard.
Resilience-to some hazard is the infrastructure’s capacity to quickly and efficiently adapt to and recover from a damaging event. Resilience usually involves
change, because if a failure occurred in the system, the system often needs to be
redesigned. Resilience of hard infrastructure is aided by its redundancy, diversity,
(in)vulnerability, and by the effectiveness of the governing soft infrastructures.
Couplings between layers are points of contact between different types of
infrastructure—like where the power grid runs water pumps, or where a utility’s
staff act to maintain or restore a water pump. These couplings are key functional
B. L. Ruddell et al.