More than 5 million miles of paved roadways criss-cross the U.S. Nearly all of them feature some form of pavement markings.
Because these markings are so inherent to our roadway infrastructure, it is easy to overlook the significant investment being made by departments of transportation (DOTs) to ensure that these delineations are in place and help offer safer driving conditions.
Worn and swaying
Road striping performs a critical function to safely guide motorists. Markings provide traffic control, convey boundaries, lane dimensions, orientation and traffic direction. Since their inception in 1911, pavement markings have communicated important navigational data to drivers with only simple variations of color, orientation and width.
In the past century road networks have expanded, vehicle capabilities have improved, traffic has increased and driving speeds have risen. As a result, more is expected of our pavement markings than ever before to provide visibility during the day and night and through all seasons. Studies have shown that effective pavement markings can reduce highway collisions 8% to 36%, depending on traffic and application.
With greater traffic volume than ever before, pavement markings are more quickly worn away. More than ever, we are learning that a worn line is a dangerous line. According to the U.S. DOT, in the past eight years approximately 42,000 people died on American roads per year. In 2008, the American Association of State Highway & Transportation Officials (AASHTO) reported that approximately 25,000 fatalities, or nearly 60% of highway fatalities a year, are attributable to lane departure, both run-off-road and head-on collisions.
While there are a multitude of factors contributing to these accidents, effective pavement markings have proven to significantly minimize their occurrence.
Lack of funding is forcing DOTs to find cheaper alternatives to durable striping. Short-term solutions require multiple reapplications to make up for the rapid decline of their performance. These same short-term solutions come with the added burden of short-term service life, resulting in greater cost over time and frequent disruption of traffic. Add to this that when pavement markings become worn and are unable to properly guide motorists, the risk to drivers increases, and the results can be devastating.
Our aging roadways need new technologies and products that address this challenge and can demonstrate significant improvements both for long-term durability and sustained retroreflectivity. Ideally, these new technologies also would include pricing solutions that ensure elevated performance and safety within DOT budgetary restrictions.
Right stripes
The Federal Highway Administration (FHWA) has been setting regulations for traffic markings since the early 1920s. Through the years, it has developed the Manual on Uniform Traffic Control Devices (MUTCD), which defines the standards used by road managers nationwide to install and maintain traffic-control devices and markings on all roads open to public traffic. To comply with the MUTCD, DOTs need to consider the visibility of the markings being used, and in the near future the retroreflectivity of the markings. DOTs incorporate several key factors from the MUTCD metrics to determine the appropriate striping system. These include visibility during daytime, nighttime (retroreflectivity) and wet weather.
Daytime visibility
Sun glare can cause the asphalt or concrete to appear to be the same color as the pavement markings, making the markings nearly indistinguishable from the driving surface and ineffective at directing traffic at normal driving speeds. Add to this the facts that concrete is light in color and asphalt has a tendency to gray or lose its color over time. To correct the lack of definition between the markings and the roadway, it is recommended to create a contrast effect by incorporating black underneath or alongside the yellow or white marking system.
Nighttime visibility (Retroreflectivity)
Studies have consistently shown that nighttime driving is disproportionately dangerous to daytime driving. Half of all fatalities occur during nighttime hours, even though nighttime driving accounts for one quarter of total driving hours. While there are a number of factors that contribute to the danger—such as fatigue or intoxication—visibility plays a significant role, because at night drivers rely almost entirely on pavement markings to direct traffic and indicate lanes, centerlines and edgelines.
Headlights and street lighting help to illuminate the roadway, but they are often not enough to meet the needs of drivers. For this reason, the MUTCD states that all pavement markings shall be retroreflective or have adequate ambient lighting to be visible. To satisfy this need, reflective glass media is embedded into the stripe itself. Light from a car’s head beam shines on the line, and the reflective media reflects the light back toward the driver, causing the marking to appear backlit.
In the past decade, a particular focus has been placed on nighttime visibility for road markings and signage, significantly raising the standards of safety for nighttime visibility. As a result, there are now new requirements for performance, testing and replacement of road markings, all of which help to offer increased safety. Today, striping manufacturers offer various reflective media options to meet state DOT retroreflectivity requirements.
Wet-weather visibility
In rainy conditions—especially at night—water obscures road markings and can negate their retroreflectivity. Unless the striping contains high-index refractive media that is capable of cutting through the water, driver visibility is greatly reduced when water covers the stripe.
While there is little that can be done when pavement markings are completely covered by snow or heavy rain, it is obvious that a poorly performing line will only worsen in adverse conditions, while a high-performing line should offer some value to drivers. Although not a striping material, per se, raised pavement markers (RPMs) have been the most common and effective solution for wet-weather visibility.
Retroreflectivity responsibility
DOTs recognize that the safety benefits of effective road markings are invaluable to maintaining a safe driving environment for the public. As the final authority on selecting, purchasing and maintaining marking installations, it is the DOT’s responsibility to make necessary improvements within the allocated budget, while minimizing disruption to the public and traffic. In 2007, it was estimated that states spent roughly $2 billion annually on installing and maintaining pavement markings. In many cases, this spending typically did not allow for the replacement of markings as often as would be desired.
A recent report showed that pavement markings create an average benefit-to-cost ratio of 60-to-1, so the value markings create is clear. In order to offer the desired performance and stay within budget, DOTs need new high-performance solutions that can last for years without the continuous expense of maintenance.
Fortunately, there are new technologies and solutions available, such as asset preservation systems. Asset Preservation for Pavement Safety Marking, by Poly-Carb, is a polymer solution that provides DOTs with the option to maximize road safety while minimizing costs through a pioneering investment management practice of purchasing guaranteed performance for up to six years.
Rather than purchasing a specified system, this model of asset preservation focuses on buying the desired performance and holding the manufacturer accountable for delivering that level of performance, regardless of the environmental and usage conditions.
In order to adopt this performance model and see the savings, DOTs need to shift the paradigm when arranging new contracts to consider all of the factors—the costs for installation, maintenance, performance, durability and traffic disruption of a traditional offering, as compared with a single long-term investment in asset preservation—a high-performance system that offers guaranteed durability, retroreflectivity and day-night visibility. Over the same period of time, asset preservation becomes the clear choice in terms of cost, overall performance and safety.
DOTs are faced with a budgetary challenge as today’s conditions result in the need for increased maintenance. Average daily traffic is a contributor, but so is intensity and frequency of rain, quality of applications and the condition of the underlying pavement. All of these factors contribute to the deterioration of pavement markings and poor retroreflectivity.
The simple fact is that when traditional markings deteriorate, no manufacturer or installer is accountable for them or their lackluster performance. The DOT then becomes responsible for all associated cost for repair: new material, removal, installation and closures.
Under the asset preservation model, pavement safety markings are regularly tested to ensure that the markings meet the required durability, retroreflectivity and day-night visibility metrics. The asset preservation model is the solution to effectively relieve the budgetary stress on DOTs, while offering long-term performance and safety on roadways.
A lifetime guarantee
A recent project with the Missouri Department of Transportation (MoDOT) highlights the value of the asset preservation solution.
In 2008, Poly-Carb of Dow Formulated Systems began a $6.5 million partnership with MoDOT to protect more than 250 miles of roadway with its Asset Preservation for Pavement Safety Marking System. Missouri was looking for a safety-markings solution that would be cost-effective and also deliver uninterrupted high performance for multiple years, regardless of harsh weather conditions, wear and tear or snowplows.
Using the asset preservation system, Poly-Carb is able to offer guaranteed visibility of pavement markings in metropolitan Kansas City and St. Louis in day, night and wet conditions for the next four years, without the need for any DOT expenditure, repair or otherwise.
The asset preservation system is able to retain its high reflectivity throughout the life of the system because of strict manufacturing quality control, polymer chemistry, including an advanced binder and glass media blend, and high-quality installation that takes into account variable weather and traffic conditions. These efforts result in a solution that requires no further maintenance.
Prior to installation, the supplier performs a thorough inspection of the roadway substrate to determine if removal is required, and if necessary, which removal method to use. In the case of Missouri, previous markings were removed and new markings were installed with plural component equipment technology.
All roadways of the Missouri contract (250 miles in total) passed initial requirements. SR-364 in St. Louis is now in its second winter season. After a full year, retroreflectivity readings for the system applied on this route exceed the performance standards as required by MoDOT.
Retroreflectivity and visual appearance inspections of the asset preservation system are tested annually by the MoDOT, Poly-Carb and an independent agency. Retroreflectivity measurements are taken with a mobile retroreflectometer calibrated to industry standards.
Asset preservation is providing MoDOT with budget flexibility, quality assurance and accountable performance.
“To maintain our infrastructure system of 33,000 miles of roads and 10,000 bridges in Missouri, we need companies that consider our challenges and develop customized solutions that meet our unique needs,” said Kevin Keith, chief engineer for MoDOT. “[The asset preservation] approach has provided MoDOT with an advanced technical system that has exceeded our performance expectations and delivered real, long-term investment value that meets our restrictive budgetary requirements.”
The project with Poly-Carb is just one of many that MoDOT has undertaken in the past four years to combat lane-departure accidents. Over most of its major highways, and high-risk minor ones, MoDOT also added signage, rumble strips, guardrail and safety edges to improve safety.
As a result of its programs, MoDOT was rewarded with a 25% reduction in lane-departure fatalities from 2005 to 2007.
Seeing down the road
With increasing traffic demands on infrastructure and our current economic conditions, it is clear that we need a 21st century solution to this 21st century infrastructure challenge in order to offer increased safety on our roadways. With offerings like asset preservation, agencies like MoDOT are leading the way and are marking a safe path ahead for others to follow.
