With billions of tax dollars being spent around the country on maintaining pavement infrastructure it is important to know how to spot a road in need of repair, before those repairs become critical and expensive. Some road rehabilitations are far cheaper than others and can help prolong a pavement segment’s lifespan while sensibly optimizing a city’s budget.
The most important things to recognize when doing a visual survey of a street are the types and quantities of pavement distresses that are present. The distresses measured can reflect the rehabilitation method that is best suited for each road segment. They can also provide a glimpse into the future condition of a roadway if it does not receive any rehab treatment. So, what are the different types of pavement distresses and how do they impact the overall lifespan and cost of rehabilitating a road?
For the purposes of pavement analysis certain types of distresses may have a more drastic effect on the overall pavement quality score.
Types of Pavement Distresses
There are several different pavement distresses that are identified by the ASTM (American Society for Testing and Materials). These are separated into two categories, Load Associated Distresses (LAD) and Non-Load Associated Distresses (NLAD).
Below is a collection of the eight most common distresses that may be present on asphalt streets:
Raveling – Raveling is the loss of fine aggregate materials on the pavement surface measured by the severity and number of square feet affected. This is an NLAD caused primarily by normal weathering. This distress is also commonly found in areas where there is heavy traffic around a turning area and the friction of tires can cause the surface materials of the road to come loose. Raveling reduces the friction of tires and increases roughness on the pavement surface. Raveling can spread very quickly.
Bleeding – Bleeding is the presence of free asphalt binder on the roadway surface caused by too much asphalt in the pavement or insufficient mixing of the aggregate materials. The result is a pavement surface with low skid resistance, especially when wet, and is measured by the amount and severity of the area. This is an NLAD that is commonly found in wheel paths.
Alligator Cracking – Alligator cracking or fatigue cracking is quantified by the severity of the failure and number of square feet. Even at low extents, this can have a large impact on the condition score as this distress represents a failure of the underlying base materials. It is one of the most common types of LAD and can spread rapidly if left unchecked.
Edge Cracking – Though edge cracking only appears on streets with unpaved shoulders, it can also be a sign of severe weakening of the pavement base. Edge cracking commonly occurs on rural roads without sufficient drainage. This allows water to seep under the surface of the street and begin eroding away at the base. Edge cracks may start forming from just outside the wheel path along the shoulder, but may spread very rapidly to the center of the street where much more damage will result in the form of alligator cracks and potholes. Drainage should be properly established so water cannot seep under the surface of the pavement.
Wheel Path Rutting – Starting at a minimum depth of ¼ inch, wheel path ruts are quantified by their depth and the number of square feet encountered. Like alligator cracking, low densities of rutting can have a large impact on the final condition score. This is a LAD that is caused by vehicle movement shifting the underlying pavement materials and is considered a pavement distortion.
Potholes – These are commonly seen in areas with lower structural standards and poor drainage where an already present distress, such as alligator cracking, have filled up with water enough that the soil beneath the pavement has begun to erode. Combine this erosion with continued pressure from street traffic and the surface asphalt is forced out of place. This creates a hole in the pavement where the asphalt surface is completely missing. Potholes are measured in severity from low at less than 25mm to high at over 50mm. Potholes can grow and become very dangerous if left unattended to. They can severely damage tires and vehicle suspensions, and even cause serious accidents. Potholes themselves are a NLAD but they are also usually a symptom of a much greater problem with the pavement base.
When assessing the overall condition of a roadway, taking notice of these common pavement distresses is key. Not only can these distresses help you to ascertain the remaining life in a roadway’s base, but they also reveal the types of rehabilitation treatment that may best suit a particular segment.
Here is a short list of the above distresses and their recommended rehabilitation treatments:
If you are interested in pavement management, check out our article on the Advantages of a Well-Maintained Pavement Infrastructure. Learn a few of the social, economic and quality-of-life benefits that come with good quality roads.
Nationwide, billions of dollars are invested in roadway networks by municipal, state and federal governments. It is not uncommon for the smallest municipalities to spend upwards of 1 million dollars per mile of roadway. This means that even very small municipal districts could be sitting on a 100 million dollar infrastructure asset that needs to be maintained. A roadway network that is taken care of properly will provide many economic and social advantages to a city, as well as its people.
Roadway networks form the economic backbone of a community. They provide means for goods to be exchanged, commerce to flourish and commercial enterprises to generate revenue. Higher pavement network quality is strongly correlated with increased household incomes, and provides a valuable incentive to attract new businesses and other outside investments.
On top of the economic boons, the social benefits of a well-maintained pavement network cannot be overstated. Increased social integration promotes diversity, a greater sense of community, and reduced income inequality throughout a city.
Roadways Drive Investments
The quality of the roadway is likely among the first things a visitor will notice upon touring a city. First impressions are important, and each and every visitor should be seen as a potential investor in the community. Pavement segments that have an aesthetic appeal are likely to draw increased investments such as high income residential neighborhoods and more high-end shopping districts. Likewise, a well maintained industrial network will attract large investments in factories and other major job creators. Balancing the maintenance of these networks with limited budgets is a major challenge that all municipalities face.
Impacts of a Degrading Network
The devastating impacts of a deteriorating and improperly maintained pavement network are anything but subtle, and can actually take quite a toll. Poor road conditions increase fuel and tire consumption while shortening intervals between vehicle repair and maintenance. In turn, these roads result in delayed or more expensive deliveries for businesses and consumers. This can lead to rapid divestment from industry and residents in your city; the consequence of which is difficult to quantify and may take decades to completely recover from.
Neglect of a pavement network could also put your city in the crosshairs of multiple civil lawsuits from personal injury or even a failure to comply with ADA standards. When cutting transportation budgets, local governments should be aware of the adverse consequences that may bring about important and unanticipated welfare effects on a community, damaging the social fabric of a city through the mismanagement of pavement.
Letting your pavement infrastructure funding slide can send you down a slippery slope of greater investment requirements over time and reduced service to the public. As a segment of pavement ages, aesthetic defects begin to give way to load associated distresses. Load associated distresses, such as alligator cracking or wheel path rutting, are directly related to traffic loading and structural capacity. The appearance of these pavement distresses indicates that the base structure of a road is beginning to fail, and much more expensive rehabilitation activities will be needed to restore the road to good condition and prolong its lifespan.
Doing it Right (for) the First Time
A well-managed pavement network brings a high level or service and pride to a city. This in turn attracts investments in business and industry, as well as fosters a healthy, diverse and prosperous community. Conversely, a poorly maintained pavement network suffers from an increasingly unmanageable deteriorating asset, poor service to a community and divestment from local businesses and industry.
Governments at all levels must wake up to the importance of a proactive maintenance approach when dealing with their pavement network. A city’s pavement network is akin to a circulatory system through which your community lives and breathes. The impacts of choking that system should not be taken lightly.
If learning about the advantages of well-maintained pavement got your blood flowing, check out our article, "How to Spot a Failing Asphalt Street". Learn how you can recognize a street that is in serious need of repairs.