Pavement Preservation:

Posted by in Uncategorized

Introduction:

If it’s not broken, don’t fix it.  It’s a popular cliche that, in the current economic climate especially, holds significant bearing on how people spend their money.  In an attempt to stretch dollars already spent, there is a tendency to postpone maintenance until the last possible moment.  For example, a car driving down the road with squeaking brakes.  So long as they aren’t grinding, the driver is content wearing the pads right down to the rotors.  Or the person with a toothache that puts off seeing a dentist until it is unbearable.  Even though the tooth is uncomfortable, so long as it’s tolerable, it can wait.  While the subjects in these hypothetical situations can keep a few extra bucks in their pockets for the time being, the implications of putting off such issues can be much more expensive than adhering to a proactive, routine maintenance approach.  Eventually, the driver with worn brake pads will begin to wear into his rotors, requiring immediate repairs costing twice as much as brake pads alone.  The person suffering from a toothache will eventually find out what was initially a simple filling procedure now requires a more expensive root canal.  In retrospect, an investment at the first sign of deterioration would have been much cheaper, not to mention less painful.
The same principle applies to road maintenance.  As much as commuters are annoyed by poor roads, most loathe infinitely more the construction induced traffic jam.  What most commuters don’t take into consideration is the sheer size of the road systems they use every day.  The United States has 3.95 million miles of public roads, with an estimated worth of a massive $1.75 trillion.  Traditionally, a “worst-first” approach has been applied to pavement maintenance.  Referred to as reactive maintenance, this philosophy prescribes to fixing roads once significant structural damage has already been incurred.  The end result necessitates more severe rehabilitation projects that are expensive, cause significant traffic delays, and unsafe road conditions prior to completing such repairs.

There is, however, a proactive solution to maintaining roads: Pavement preservation.  The National Center for Pavement Prevention defines pavement preservation as “a cost-effective set of practices that extend pavement life and improve safety and motorist satisfaction while saving public tax dollars.”  Essentially, a pavement preservation program seeks to create a system of implementing relatively small scale repairs on roads prior to structural degradation to avoid the necessity of full blown road reconstruction.  Successful pavement preservation will result in long term savings, reduced traffic congestion, and safer roads.  This essay will discuss the fundamentals of pavement preservation, the techniques used for pavement preservation, and discussion of current pavement preservation practices; finally, an objective analysis of the benefits and criticisms will lead to a conclusion.

Pavement Preservation Fundamentals:
While the techniques of pavement preservation are pivotal, as will be discussed in the following section, for any pavement preservation program to succeed there are several philosophical and strategic elements that must be determined prior to taking any maintenance measures.  First, and foremost, is embracing the philosophy of pavement preservation; the traditional mentality of “worst-first” repairs needs to be replaced with one of prolonging the investments already made to road systems.  Pavement preservation needs to be seen as a long term process.  A short term analysis may suggest that preservation based maintenance is an unnecessary expenditure, but in the long run up to six dollars can be saved for every one dollar put into pavement preservation, a significant amount considering the cost of maintaining road ways.

Once the philosophy of pavement preservation is embodied, strategies must be developed to execute a successful preservation program, certain questions must be answered: How can dedicated funding be secured?  How can quantifiable data be collected to both account for present road conditions and to monitor the program’s success?  How and when should actions be taken to efficiently prolong the life of the current road systems?  Unfortunately, there are no universal responses to any of these questions, they are unique to every individual road management agency; there are, however, some basic points to consider when making these decisions.

Without dedicated funding, pavement preservation projects frequently get pushed to the last tier of priority, and a variety of factors from backed up “worst-first” repairs to severe weather can be enough to sabotage an entire pavement preservation program.

First, there is a difference between funding and dedicated funding.  Without dedicated funding, pavement preservation projects frequently get pushed to the last tier of priority, and a variety of factors from backed up “worst-first” repairs to severe weather can be enough to sabotage an entire pavement preservation program.  A common phrase when discussing pavement preservation is “applying the right treatment to the right pavement at the right time,” and if preservation projects are delayed, roads can incur structural damage in that time, making any attempt to preserve the road obsolete.  This being said, finding ways to eliminate competition for funds is essential to ensuring proactive measures.

Data collection and management is also crucial to a successful pavement preservation program.  Data provides a quantifiable means of assessing road ways and the preservation program as a whole.  Again, the means of collecting such data is in the hands of the agencies managing the roads, but the end objective is simple: Provide precise and unbiased information that can be used to determine when preservation measures should be taken and how effective previous maintenance actions were.  There are various indexes that can be used to quantify road conditions, including the Pavement Condition Index (PCI, measured visually on a scale from 0 to 100), the Present Serviceability Rating (PSR, measured by quality of ride on a scale from 0 to 5), and the International Roughness Index (IRI, measured by the vertical deviation of a vehicles suspension in units of millimeters per meter).  Regardless of what method is used to quantify data, it is important to be consistent and use it effectively.

Finally, there is determining where and when to implement pavement preservation techniques.  Successful pavement preservation programs need to be efficient and effective.  Again, the saying about the right treatment, the right pavement, the right time has significant value.  Maintenance to prolong road life must be executed with precise timing.  As mentioned before, putting off maintenance to preserve road ways can lead to a “too little, too late” situation; once the structural integrity of a road is compromised, reactive maintenance is necessary.  Similarly, executing preservation techniques too early will result in a waste of time, money, and resources, all of which could have been used for a more appropriate preservation project.  Taking these two points in to consideration, there is a specific window of time when preservation techniques are effective and efficient.  By identifying when such a time span will exist on specific road segments, road management agencies can coordinate and facilitate several preservation projects, optimizing their production factors, and, sequentially, optimizing their pavement preservation program.

Pavement Preservation Techniques
The maintenance techniques used for pavement preservation are unique from reactive maintenance in that they are significantly smaller scale projects, focusing primarily on a road’s surface rather than structure.  These techniques prolong the life of road ways by addressing surface imperfections before they are allowed to deteriorate the subsurface structure of the road.  Even though there is no way to make pavement last forever, addressing minor issues significantly reduces the wear on the road’s structure.  The maintenance procedures used for pavement preservation are formally categorized into three categories: Routine maintenance, preventive maintenance, and minor rehabilitation.  Though the actual techniques that fall into each specific category are different, their objectives are the same; they attempt to make existing road systems last as long as possible.

As defined by the American Association of State Highway and Transportation Officials (AASHTO), routine maintenance “consists of work that is planned and performed on a routine basis to maintain and preserve the condition of the highway system or to respond to specific conditions and events that restore the highway system to an adequate level of service.”  As the name implies, routine maintenance are tasks that are planned and performed on a regular basis.  These various maintenance techniques include surface cleaning and clearing of debris, maintaining lane lines and other various pavement markings, and minor surface repairs such as filling cracks, patching potholes, or small scale overlays.  While not all routine maintenance techniques are strictly considered to be a part of pavement preservation, they will fall into this category when used to specifically to prolong the life of a road.

Preventive maintenance is the most intuitive component of pavement preservation.  It is defined, again by the AASHTO, as “a planned strategy of cost-effective treatments to an existing roadway system and its appurtenances that preserve the system, retards future deterioration, and maintains or improves the functional condition of the system.”  These techniques are the primary tools used for pavement preservation.  They include tasks that are specifically implemented with the intentions of protecting the investment made in already constructed roads by addressing surface flaws that threaten to jeopardize the structural integrity of the subsurface, essentially preventing reactive maintenance.  Preventive maintenance includes multitude of procedures, including sealing cracks, chips, or joints, slurry seals, and thin asphalt overlays.  In short, preventative maintenance aims to address problems as they form so that minimal input of time, money, and resources can be used to prevent a larger problem in the future.

Minor rehabilitation is a subset of a more general category of maintenance called pavement rehabilitation.  Pavement rehabilitation is defined by the AASHTO as “structural enhancements that extend the service life of an existing pavement and/or improve its load carrying capacity.”   The distinction between minor and major rehabilitation is fairly straightforward; minor rehabilitation does not involve structural enhancements, as opposed to major rehabilitation.  Minor rehabilitation is often more drastic from preventive maintenance, frequently addressing a more deteriorated surface, however, since it does not involve repairs to the structure and instead aims to prevent structural damage, it is classified as an element of pavement preservation.  Restoration treatments and larger scale overlays fall into the classification of minor rehabilitation.

Current Pavement Preservation Practices
As long ago as 1997, the AASHTO released a survey revealing that most state highway agencies embraced the notion of pavement preservation.  As nearly half of the interstate system at the time was considered to be in sub par condition, it is no surprise that the principles of pavement preservation began to be taken more seriously as a practical solution to the always deteriorating highway system.  Several states went on to implement such a plan, with some of the most successful being California, Georgia, Michigan, and Texas.  While the benefits were not noticeable immediately in the short term, in time the results of utilizing a pavement preservation program proved quite favorable.

These states realized a variety of benefits, as reported in a 2000 publication by the Federal Highway Administration.  Texas found it to be comparatively inexpensive and gradually improving the overall status of their road systems.  Georgia also noted an improvement throughout their collective highway systems and also found that the transition from reactive maintenance to preservation projects was fairly seamless, hassle free, and had little effect on their ability to tend to larger scale repairs.  California estimated that they were getting about five to seven additional years of usage out of their already existing highways.  Michigan concluded that preventive maintenance was nearly 14 times cheaper than reactive maintenance per lane-mile; they figured, in eight years of practicing pavement preservation, they had saved in excess of $700 million in comparison to using reactive maintenance.

As pavement preservation programs are adopted by new agencies and refined by those already using such programs, there is increasing demand for better materials with more efficiency, versatility, and eco-friendly.  As both road management agencies and material manufacturers continue to improve, so too will the benefits of pavement preservation.

Criticisms and Conclusion
As established by the reports of agencies using pavement preservation programs, the advantages of a proactive, preventative approach to road maintenance has proven to be as successful in practice as it is in theory.  It costs less, produces less traffic congestion, and makes roads safer longer.  It is a curious concept that such a philosophy is not universally embraced.  While the premise of pavement preservation maybe strike some as straightforward and logical, there are certain criticisms that stand in the way of a universal acceptance of the concept.  The public may have difficulty understanding why they are waiting in traffic while a construction crew repairs a relatively small imperfection.  The layman will not understand the consequences of allowing what he deems a superficial crack in the road go unattended to.  Also, like any change in an organization, accepting change is difficult.  Convincing every component of an agency, from the stakeholders to the work crews, that they need to change their ways poses the epic task of shifting paradigms.  Finally, the nature of the research data used to assess the performance of a pavement preservation program is not concrete.  For example, asserting the financial benefits of a preservation approach over a reactive approach requires that a hypothetical projection be made for how maintaining a reactive approach “could” have been.  Certainly historical figures or comparisons to similar systems could be referenced, but ultimately, because of the unique circumstances of every agency, there can be no true comparison without speculation.

Still, the enticing elements of a pavement preservation program exist.  Despite criticisms, several road management agencies have implemented a preventative approach with great success.  Research surveys show an increase in the general public to support a more financially sound model, as opposed to the “worst-first” model.  As the concept of pavement preservation is better understood, the more and more support it receives.  While states like Texas, Georgia, California, and Michigan reap the benefits, others continue to implement dated models of reactive maintenance.  Taking all of this into account, there is one question that needs to be answered: Aren’t the long term benefits of pavement preservation worth the investment in being proactive?

 
References
The National Center For Pavement Preservation
http://www.pavementpreservation.org/

Turner-Fairbank Highway Research Center
Article: Pavement Preservation: Preserving Our Investment in Highways
http://www.tfhrc.gov/pubrds/jan00/pavement.htm

Washington State Department of Transportation
Article: Pavement Evaluation – Roughness
http://training.ce.washington.edu/wsdot/Modules/09_pavement_evaluation/09-2_body.htm

US Department of Transportation – Federal Highway Administration
Memo: Pavement Preservation Definitions
http://www.pavementpreservation.org/library/getfile.php?journal_id=482

Foundation for Pavement Preservation
Article: Pavement Preventive Maintenance Guidelines
http://www.fp2.org/pdffiles/PavPrevMainGuides.pdf