Educational Tool Kit Inserts

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In my articles in April’s eTxAPA Newsletter I discussed the Educational Tool Kits and Brown Bag Lunches. Please let me know if you need any Tool Kits for visits you may have planned with local cities, counties and consultants. Also please let me know if you want to hold a Brown Bag Lunch as a follow up to one of your visits to these same entities.

This month I want to start a series of articles that will span the next several months in which I discuss the inserts in the Educational Tool Kit and why they are important. This month I want to start off with an insert developed by the APA entitled "Smoothness Matters."

In "Smoothness Matters" the APA explains that the biggest difference one can make in improving fuel economy in existing vehicles is to build smooth pavements. This would seem to make sense; however, there are some out there that believe that other factors could be more beneficial. They believe that rolling resistance and pavement stiffness have a bigger impact on the fuel economy of existing cars on the road today. That simply is not the case.

"Smoothness Matters" explains that lower fuel consumption conserves natural resources, and since America has more than 2.5 million miles of paved roadways that even a slight change in fuel economy per vehicle could have a dramatic effect. It then goes on to explain that of the three pavement characteristics that have been studied (rolling resistance, pavement stiffness, and pavement smoothness) pavement smoothness can have the greatest effect on the fuel economy of existing vehicles.

Reputable studies have shown that rolling resistance could account for increased fuel efficiency by 1 percent or less. Rolling resistance is the loss of vehicle energy due to contact between the tires and the pavement. Studies have shown that when compared to other factors such as wind resistance the loss of vehicle energy is small.

Reputable studies have shown that pavement stiffness could have a minimal effect on fuel efficiency. Pavement stiffness, an indicator of strength, accounts for between 0.005 to 0.5% difference in fuel consumption. With these percentages you can see how the effect of pavement stiffness on fuel economy is minimal at best.

On the other hand, pavement smoothness can account to an increase in fuel efficiency of 5% or more. This smoothness affects the rolling resistance by influencing the friction between the tire and the roadway. FHWA, at their WesTrack pavement test track in Nevada, showed that trucks running on only a slightly smoother pavement could reduce their fuel consumption by 4.5%. Other studies have confirmed this and have even showed that the savings could be as much as 10% by rehabilitating the roughest pavements.

Smoother pavements also reduce vehicle-operating costs and driver fatigue by minimizing tire bounce and load impacts. Studies have also shown that smoother pavements last longer. One such study shows that by improving pavement smoothness by 25% can extend the life of that pavement by almost 10%.

The cement/concrete industries have in the past and will continue in the future to make claims that concrete pavements save fuel. With 94% of America’s highways paved with asphalt it is had to accurately make a comparison. Such comparisons would require a tightly controlled experiment. The cement/concrete industries have sponsored research projects over the years and will continue to do so. The problem with all of their studies to date is that they compare apples to oranges by using pavements that are not equivalent. These studies have helped to reinforce the WesTrack study that showed it is pavement roughness, not pavement type that can have the biggest affect on fuel economy.

Asphalt roadways are simply smoother. Almost all states have smoothness standards for their newly built roadways and some states even have different standards for concrete and asphalt roadways. States that have different standards actually hold asphalt roadways to a higher standard.
Another factor in smoothness is routine maintenance. While roadways of both types can be built to virtually last forever they all will eventually need some routine maintenance. Routine maintenance of asphalt roadways typically amounts to infrequent milling of the surface for recycling followed by placing a new smooth surface that will last another 12-20 years.

Americans burn 175 billion gallons of fuel driving 3 trillion miles every year. By making the nations roadways slightly smoother fuel consumption could be reduced by 4%, which amounts to about 7 billion gallons. That ends up being equivalent to taking 10 million vehicles off of the roadways each year.

So the bottom line of the Educational Tool Kit insert, titled "Smoothness Matters," is that the smoother the pavement, the less fuel consumed by the vehicle. Please take the time to read this insert in your tool kits. All of the information I used above came directly out of this insert. If you don’t have a tool kit or if you just want a copy of this insert please let me know. I will be happy to get you copies of whatever you need.

Until next month remember, "Smoothness Matters."