You may not realize it if you have not been involved in public works for very long, but the pavement network that runs throughout your city is the most valuable visible asset that your city owns and maintains. Because the utility of this asset is so great and it is constantly deteriorating from use, it is very important to understand proper pavement management processes.
The pavement assets managed by your city require constant upkeep. In order to assess the need in your network, a dedicated pavement management process is necessary. This requires pavement management software, GIS integration, high tech survey equipment, and dedicated personnel. Most municipalities will hire a pavement management consultant with expertise unique to the city’s needs.
Here are some of the most common mistakes cities and counties make that end up misusing millions in tax payer dollars:
In pavement management the term backlog refers to streets that cannot be rehabilitated without partial or complete reconstruction. Because reconstructing a street is much more expensive than placing a seal or an overlay on the surface, pavement segments that fall into the backlog category are often deferred until the funds are available to dedicate towards such projects. The constant deferral of these projects can lead to a build-up of a network’s backlog streets until it reaches an unmanageable state. The figure below illustrates how a proper pavement life cycle should look.
A network is treading into precarious territory when the backlog exceeds 15% of the total pavement network. Once a network's backlog exceeds 15%, the cost of reconstruction projects begins to eat up large portions of the budget that would otherwise be used for preventative care. This spirals into a situation where pavement segments fall into the reconstruction category faster than the city can repair them. This situation can be devastating to a city’s budget and can ultimately bankrupt a public works department.
Many public works departments that have little experience in pavement management will make the mistake of always scheduling rehabs through a worst-first methodology. Municipalities that have a “worst-first” pavement management philosophy often spend far too much of their limited budget on reconstructing segments of roadway. This is where the pavement management lifecycle curves seen below is important to understand.
The figure below illustrates how pavement that has degraded to “poor and very poor” categories is much more expensive to rehabilitate than the preventative maintenance on streets in the “good and very good” category.
Municipalities should focus the majority of their budget on less expensive preventative maintenance. This will prolong the lifespan of these roads and prevent them from falling into the more expensive rehabilitation categories. Notice the quick decay in pavement quality when preventative maintenance methods are not followed.
This is similar to the notion of applying oil to a vehicle, rather than waiting until the engine needs to be replaced. The oil need is more frequent, but the cost savings over an engine rebuild is dramatic.
Need Year Rehabs:
The need-year is a segment’s last possible year that it can benefit from a particular type of rehabilitation. Understanding the concept of need-year is very important for optimizing your pavement management budget. This process is almost impossible to track without dedicated pavement management software that can select the ideal year for a rehab to take place. The rationale of embracing the need-year concept is that a municipality can know when deferring a rehabilitation project is appropriate and will not result in a dramatic increase in cost.
The ideal is to defer rehabilitation on a street as long as possible without increasing the cost of the maintenance on that segment. This allows the municipality to focus repairs on streets that will become more expensive to rehabilitate if put off for any longer, thereby optimizing limited annual funds.
Ignoring Signs of Pavement Base Failure:
Often times, streets that require more expensive rehabilitation efforts are in areas where a portion of the road’s base is failing. When the base of a street begins to fail there are often some clear signs that come in the form of load associated distresses. A load associated distress is a type of crack or other pavement distress that reflects on the overall structural integrity of a pavement segment. Read more about Load Associated Distresses HERE.
The most reliable way to measure the structural strength of a pavements base is to do what is known as a deflection test. A deflection test is done with specialized equipment that applies moderate weighted stress to a pavement section and measures the amount of feedback. This can be used to calculate a structural integrity score for a road and determine the type of rehabilitation technique needed to return it to complete service. Pavement engineers can also use this type of data to make more accurate predictions about the future quality of a street.
It is important and extremely cost effective for municipalities to routinely conduct structural testing on their high-traffic roads to avoid the exaggerated cost associated with a sub-optimal rehabilitation plan.
Misjudging Rehab selection (over/under-repair):
A street that is paved over without regard to the strength of its base is likely to receive a sub-optimal treatment that does not utilize a city’s limited budget in the most efficient way. Even worse, a street that receives too light of a rehabilitation may see a rapid decline in pavement quality leading to greater rehabilitation needs in the near future. Such is the importance of a pavement management system that identifies the proper rehabilitation techniques using the most accurate possible data.
The only way to get that data is through a laser road survey and a proper pavement management system. The collection and organization of this data is the primary reason why municipalities hire pavement management companies like IMS.
(Bonus) Under Budgeting:
Under budgeting pavement infrastructure is a nearly ubiquitous problem for municipalities throughout the country. From public works departments that continually kick the can down the road, to politicians that divert pavement management funds for other purposes; chronic pavement infrastructure under-funding has led many municipalities down a tragic path of financial destitution.
Our paved road systems are the one of the most utilized and valuable components of our nation’s infrastructure. If we cannot recognize the need to invest in such assets, perhaps it is time again to invest in the rearing of horses for our future transportation needs.