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Roads don’t last forever, and government dollars only stretch so far. How can communities efficiently maintain their roadway assets? A combination of pavement condition surveys, lifecycle modeling, and pavement preservation treatments can significantly cut the cost of ownership. Condition surveys identify needs, lifecycle modeling prioritizes investments, and preservation treatments stretch each dollar further. We walk through how each of these three actions saves money and brings communities one step closer to perpetual pavement, where the base layer of a road is protected so that only the riding surface needs to be replaced.
Pavement condition surveys identify problem areas
The core of a successful pavement management program is a comprehensive pavement condition survey (PCS). This is a procedure that involves regular inspections to understand the current condition of the pavement. Through accurate and consistent pavement condition ratings, it is possible to anticipate upcoming maintenance needs. This allows for planned, budgeted maintenance instead of costly, reactionary repairs.
There are many PCS rating standards. Popular standards include ITRE, LTPP, ASTM, and PASER. There are likewise several methods for data collection, including visual, automated, artificial intelligence (AI), and hybrid. The key to selecting a standard method is to understand what data will be needed to make sound decisions for the surveyed roadway network. Holding a planning meeting to assess these needs at the beginning goes a long way toward selecting the right rating standard and methodology.
Lifecycle modeling empowers smart financial decision-making
A lifecycle model is a tool that enables communities to predict future roadway network conditions based on deterioration estimates, funding levels, and treatment types. This predictive power has three key benefits for decision-makers and stakeholders:
- Lifecycle modeling tells a clear story about a community’s roadway network. If a community has been underfunding its roadway network, then a lifecycle model will show both the present and future consequences of that underfunding. A clear downward trend in level of service (LOS), typically represented by the average pavement condition index (PCI) score for the network, can motivate elected officials to change how they invest in roadway repairs and replacements.
- Lifecycle modeling shows how to budget effectively to achieve a desired level of service (LOS). Sometimes, historic underfunding can be resolved simply by changing which repair and replacement strategies are used for the roadway network. Other times, communities need to increase their overall investment to reach the desired LOS. Lifecycle modeling helps decision-makers balance the need for investment with the community’s ability and willingness to accept rate increases. It shows how a desired LOS can be reached with different levels of investment over different time spans.
- Lifecycle modeling generates optimized annual work plans. For each type of pavement distress, there is usually more than one way to treat it. Decision-makers need to balance treatment costs against treatment benefits. Lifecycle modeling reveals the “right mix of fixes” to provide the greatest improvements in overall network condition for the available budget.
Lifecycle modeling can be used for roadway networks of any size and composition. They can be built from pavement condition data regardless of the rating standard or collection method used. They offer valuable insight for communities with generous budgets and those with modest ones.
Crucially, lifecycle modeling confirms that in a head-to-head comparison, the traditional “worst-first” approach to pavement management typically produces worse network-level outcomes than a preservation approach.
The worst-first approach, and why it doesn’t work
Many communities prioritize streets in the worst shape for repairs. This approach leads to the lowest level of service for the highest cost: the entire pavement budget is spent on rehabilitating a handful of roadway segments, leaving the rest of the network untreated. Eventually, these untreated segments end up requiring more expensive treatment such as rehabilitation or total reconstruction that eats up even more of the repair budget. A worst-first approach makes it very difficult to clear the community’s backlog of repair projects without a massive increase in spending that most communities simply cannot afford.
The strengths of a preservation approach to pavement management
In pavement management as in public health, an ounce of prevention is worth a pound of cure. Unfortunately, decision-makers may not be familiar with the range of pavement preservation treatments available, or they may not have a clear understanding of how interim investments lead to long-term savings.
The table below shows how the cost of the worst-first approach compares to the cost of a preservation approach. In the worst-first approach, one mile of 24’ wide road undergoes 2” mill-and-fill in year 17 at a cost of approximately $450,560, or $26,504 per year. In the preservation approach, the same one mile of 24’ wide road is treated with preservative techniques in years 1, 5, 10, and 17. Notably, the micro surfacing preservative technique is more expensive per year than the distributed cost of the mill-and-fill. But the total cost of the preservation approach is only $247,808, or $14,577 per year. This represents a savings of 45 percent—savings that can be invested in preserving or repairing other areas of the roadway network.
Pavement preservation treatments extend the lifespan of roads
Pavement preservation treatments have evolved significantly over the years, offering efficient alternatives to traditional pavement repair. These treatments are designed to preserve and extend the life of the pavement while being significantly less expensive than traditional methods. Rejuvenators, crack sealing, and micro surfacing can address minor pavement distresses before they develop into more significant problems.
Rejuvenators
Rejuvenators are applied to newly paved streets, typically when they are one to four years old. Rejuvenators replace some of the maltenes and other chemical binders in liquid asphalt that are lost over time from exposure to the elements. Rejuvenators preserve the plasticity and durability of the asphalt, extending its life.
Crack Sealing
Crack sealant is a rubberized asphalt material. Crack sealing is the process of applying crack sealant to cracks in the riding surface to keep surface water from penetrating to roadway base, where it can cause damage and failures in the base material.
Microsurfacing
Microsurfacing is a mixture of polymer-modified emulsified asphalt, crushed aggregate, water, and other additives. Properly proportioned, microsurfacing can correct minor rutting and improve and protect the quality of the road surface.
What about asphalt overlays and paving into the gutter?
Don’t do it. These stop-gap measures provide temporary relief with significant long-term drawbacks. First, existing crack patterns will come back after a short period of time. Second, as successive overlays are performed, they will create drainage problems and ADA compliance issues. Eventually, when the pavement reaches the top of the curb, it will require additional inches of milling and filling, which adds significant cost to the yearly resurfacing program. In the end, all of this leads to paving fewer streets and hastens the decline of the overall roadway network condition. Or, as the U.S. Federal Highway Administration (FHWA) put it in a recent report, “Today’s users are, in effect, consuming the infrastructure of their children.”
Using pavement preservation treatments in an appropriate sequence can effectively manage the pavement’s lifecycle and maximize the service years from the initial investment. In fact, experience at WithersRavenel has shown that while typical untreated pavement will last on average about 17 years, the same pavement with multiple rounds of pavement preservation treatments applied can last up to 30 years.
Toward perpetual pavement
In the past, many pavement owners accepted that pavement would ultimately reach the end of its useful life, fail, and require full-depth reconstruction. With a worst-first approach, this is true and extremely expensive. By using the preservation treatments mentioned above, pavement owners can extend the life of the asphalt riding surface and protect the pavement base.
At some point the asphalt riding surface will have to be milled up and replaced. But when the base has been protected through one or more preservation treatments, only minor base repairs should be required instead of total base replacement. This strategy of protecting the base layer and only replacing the riding surface is known in the industry as perpetual pavement, and it saves substantial money and effort on pavement management.
The bottom line
Balancing a limited budget is always a challenge. Communities can extend the life of their pavements, save money, and provide safer, smoother roads for travelers with a consistent program of pavement condition surveys, lifecycle modeling, and pavement preservation treatments.
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