"Pavement management" refers to a systematic process of maintaining,
upgrading and operating a network of pavements and involves three major
components: the pavement life cycle, the costs associated with this life cycle
and pavement management systems.
Pavement Life Cycle
All pavement will deteriorate over time. Typically, pavement
deteriorates at an ever-increasing rate: at first very few distresses are
present and the pavement stays in relatively good condition, but as it ages more
distresses develop with each distress making it easier for subsequent distresses
to develop. For instance, once a substantial crack occurs it is then
easier for water to (1) infiltrate the HMA layer and (2) penetrate and weaken
the subgrade.
Maintenance and rehabilitation are the two principal treatments used to
extend pavement life. These treatments will (1) immediately increase the
pavement condition and (2) affect the future rate of deterioration. In general, maintenance can slow the rate of deterioration by correcting
small pavement defects before they can worsen and contribute to further defects.
Beyond a certain point, however, defects become too large for correction by mere
maintenance. At this point, rehabilitation can be used to effect a
wholesale correction of a large number of relatively severe defects, which
provides a step increase in pavement condition. Figure 1 illustrates
this concept.
All new construction, reconstruction, rehabilitation and maintenance projects should employ some level of
economic evaluation to determine the most cost effective method and timing.
For instance, a rehabilitation that involves placing an
SMA wearing course may cost as
much as 20 percent more than a typical
dense-graded HMA
wearing course. However, the SMA wearing course may provide up to 40
percent additional pavement life based on its rut-resistant nature.
Life cycle cost analysis is typically done over a fixed period - often 20, 40
or even 50 years. The costs normally considered are:
Initial construction costs.
Maintenance costs.
Maintenance costs are those costs associated with maintaining the pavement
surface at some acceptable level.
Rehabilitation costs.
These costs represent the costs associated with each rehabilitation
alternative (typically they are overlay costs).
Salvage value. The salvage value is the relative value of the
pavement at the end of the analysis period. The value of any generated
RAP when replacing a deteriorated pavement should
be included in the salvage value.
User costs. User costs are those costs that are accrued by
the user of the facility during the construction, maintenance and/or
rehabilitation and everyday use of a roadway section. These costs
include vehicle operating costs (tires, gas, oil, etc.) and user delay costs
(costs associated with slow downs due to construction and maintenance
activities and denial-of-use) (Peterson, 1985). User delay costs are the most difficult
and most controversial life cycle cost to accurately calculate because they
involve assigning a dollar value to individuals' delay time and determining
future traffic conditions.
These costs are usually summarized over time by discounting all costs that occur
at different times using the present worth method to account for the time value
of money. The comparative costs may be shown as either total present worth
or an annualized cost. LCCA, the availability of funds, project
specific and environmental conditions or constraints, project constructability
and the ability of each alternative to serve the anticipated traffic volumes
should all be used in the decision process for selecting the most appropriate
alternative.
A pavement management system is a set of tools or methods that assist
decision makers in determining cost effective strategies for maintaining,
upgrading and operating a network of pavements. There are numerous
different pavement management systems (PMS) from which to choose, each one with
its own level of complexity. For a small town or rural county a simple
system based on visual inspection and maintained in a Microsoft Excel or Access
database may be more than sufficient. For a state road network a more
complex PMS is usually appropriate.
