You probably never imagined how many lives could be saved by simple pavement renewal efforts. In October, 2014 the Federal Highways Administration and U.S Department of Transportation released the results of a 10-year study on fatal car crashing in the United States. A gut wrenching 371,104 fatal crashes occurred in the U.S from 2000-2009. (FHWA, 2014) The report identifies 12.6% of these fatal accidents occurred on wet pavement. The FHWA then asserts a shocking recognition; 70% of these fatal accidents could have been prevented or minimized by simply improving pavement surface friction. That’s 32,730 lives that could have been saved by inexpensive and easily identifiable pavement rehabilitation efforts.
The most commonly deferred roads are those that display only surface distresses, such as raveling (loose pavement material on the surface) or bleeding (excess asphalt binder on the pavement surface). Although these distresses do not reflect an imminent failure of the pavement base, they do reduce tire traction and increase the possibility of a vehicle skidding.
Thankfully there are some easily implemented solutions that can alleviate these concerns and make your roads a safer place to drive.
Identifying the problem
The first step in reducing the concern of vehicle skidding is to identify areas of your pavement network where distresses related to vehicle traction are present. The most accurate and cost effective means of doing this is through a pavement network survey. The survey should collect data on asphalt streets with excessive bleeding and raveling while focusing on scaling and excessive polished aggregate on concrete streets.
Asphalts streets with excessive bleeding or raveling will suffer from reduced tire traction. Luckily these distresses are easily fixed in most cases.
Asphalt bleeding is caused when asphalt is improperly mixed and the excess asphalt binder rises to the pavement surface. If the bleeding is light it can be soaked up through a light application of coarse sand, while heavier bleeding should be shaved away using a motor grader.
Raveling is usually an effect that stems from another pavement distress, such as an improperly sealed crack or a poorly maintained patch. Asphalt streets that receive heavy snowfall may also see raveling as the result of studded tire or snowplow traffic. Usually minor raveling can be simply swept aside through a standard street cleaning processes, but if it is more severe or there are other distresses present on the road it may be more effective to rehab the entire segment with an overlay rather than continually sweep up loose asphalt material from the crumbling pavement.
Compared to the porous nature of asphalt, concrete is impermeable. This causes water to sit on the surface until it evaporates, all the while increasing the danger of skidding on the slick concrete. This is especially apparent in damp environments where sitting water is slower to evaporate from the surface. To address this aspect of concrete pavement, construction companies apply a process known as tining. This is where a metal rake creates grooves in the pavement designed to increase friction. It is important to note that time, weather and traffic will have a wearing effect on concrete tining and slowly grind down on the pavement grooves. In this case it is often most cost effective to wait until further distresses like cracks and scaling trigger a panel replacement to rehab these areas.
If replacing the concrete panel is not an immediate option, it is possible to apply a post-construction texturing to the pavement surface through the process of diamond grinding. This process requires specialized equipment with rotating diamond bladed saws and it may not be appropriate for all sections of concrete pavement.
Improving Public Safety
If your city has seen frequent snow or rainfall, or has aging pavement infrastructure, it may be pertinent to develop a strategy towards skid resistance roadways. Utilize a pavement surface survey and determine where drivers in your city may be at risk. Pavement texturing treatments are a great way to increase public safety without breaking the bank. Every life lost in a car accident is a tragic loss for our whole society. If your city takes active measures to reduce vehicle skidding, you WILL save lives.
Want to learn more about setting up a pavement management program in your city? Check out "Designing and Implementing a Pavement Management System" - An IMS Whitepaper