Green Street Calculator 

With more attention than ever being focused on energy conservation, most people have focused on vehicles as the main target for improvements.  Vehicle fuel efficiency and hybrid technology, as well as other eco-friendly improvements such as bio-diesel will help make great strides to improving vehicles and saving energy.  When it comes to energy conservation, the road surface can also make a significant contribution! 

This calculator provides a way for you to see the positive contribution concrete pavements can make as part of a “Green Streets” program.  It allows you to see how much less energy is consumed with concrete pavement than other common materials.    

What are Green Streets?

Green Streets are about more than energy consumption.  Green Streets are those that:

1)      Have superior longevity and do not require frequent maintenance or resurfacing, which in turn provides these eco-friendly benefits:

a.       Consume lower quantities of raw materials, like aggregates, steel, asphalt, cement, etc.

b.      Reduce energy consumption associated with:

                                                    i.      Raw material processing

                                                  ii.      Rehabilitation

                                                 iii.      Reconstruction

c.       Reduce congestion – a huge and needless consumer of energy, which can be avoided with more investment in road capacity and more use of stronger pavements designed for longer life spans (+25 years)

d.      Improve environmental impacts, such as air quality and carbon dioxide (CO2) associated with:

                                                    i.      Manufacturing of materials and elements for road building

                                                  ii.      Construction of the infrastructure

                                                 iii.      Congestion – again, as this is a huge consumer of energy and significant source of CO2, which could be avoided with more investment in road capacity

2)      Maximize the incorporation of industrial by-products such as fly-ash and slag cement, allowing for:

a.       Reduced disposal of these materials (taking them out of the waste-stream)

b.      Improved pavement performance and longevity, and

c.       Reduced material costs

3)      Can be effectively renewed through surface planing or grinding (extending its service life by 10-20 years) and ultimately recycled at the end of its service life, resulting in:

a.       Lower pressures on our virgin aggregate resources, and

b.      Reduced energy use as a result of fewer materials-intensive pavement resurfacing (overlay) cycles, and less need for natural stone, gravel and sand extraction. 

4)      Have a surface that reflects light and does not intensify the Urban Heat Island effect, providing  associated economic and eco-friendly benefits:

a.       Improved pedestrian and vehicle nighttime visibility

b.      Reduced energy demand for street lighting,

c.       Realization of positive CO2 offsets, and

d.      Improved air quality

5)      Have a structure and surface that reduces energy consumption by:

a.       Requiring less fuel to build and maintain the pavement

b.      Deflecting less under loads so the vehicles travel with less resistance and improved fuel efficiency

How can Concrete Pavements Reduce Energy Consumption

Concrete is the strongest of all road surfacing materials.  It is designed to be very rigid.  As a result, concrete roads do not deflect much under heavy loads, so vehicles get better fuel mileage per gallon than on any other type of surface.  Several studies have concluded that less energy is required to propel a vehicle on a rigid surface than on a flexible one.  It is analogous to rolling a bowling ball on a hardwood floor versus on a rubber mat – on which surface will the bowling ball roll farther (or with greater ease)?  Physics, as well as simple intuition, gives us the answer.

Rigid pavements, like concrete, are built in just one layer and as a result require less fuel to construct than conventional pavements made from more flexible materials, like asphalt , that are built in several thin layers.  Every layer requires more delivery trucks, passes of the paving machine, rollers, etc.  In addition, concrete does not need to be heated to mix properly, and does not need to be maintained at a high temperature during placement like flexible pavement materials.  For these reasons, a concrete roadway requires less fuel to construct.

Just how much fuel and money can be saved using concrete pavement from these two factors alone?  Use the Green Street Calculator below to see…

Your Inputs

Net Road Length ft  
Total Road Width ft (one lane is typically 12 ft wide)  
Concrete Thickness in. (typical: streets = 5-8 in.; highways = 9-12 in.)  
Comparable Asphalt Thickness in. (varies, rough estimate is 1.25 x concrete thickness)  
Asphalt Density lb/cubic ft (typically 145 lb/cubic ft for hot mix)  
Traffic vehicles/day or average daily traffic  
Percent Truck %  
Diesel Fuel Cost $/gal  
Gasoline Fuel Cost $/gal  
Road Design Life years (typical period is 30 years)  
Have Calculator Show impact

Calculated Results

Using a concrete surface in your example results in the following:

  • A reduction of on average  13,167  gallons of diesel and gasoline fuel during construction, saving on average  $32,012  in initial construction costs.  

  • Trucks will consume on average  771  gallons less diesel fuel per year and other vehicles will consume on average  8,284  gallons less gasoline per year while traversing this section, saving on average  $16,424  per year in fuel costs.

  • Over the 30  year design life you've entered, this will amount to a total savings of on average  284,820  gallons of diesel fuel and gasoline, amounting to a total savings of on average  $524,746 .  

As highlighted above, in addition to these calculated savings, there are savings associated with the longevity of the concrete pavement.  Since a concrete pavement does not have to be resurfaced on a frequent basis (8-14 years is typical for flexible pavements) the fuel savings associated with concrete pavement construction are spread over the entire 20-30 year pavement life, unlike other paving solutions where additional energy (fuel) is consumed every time the pavement needs resurfacing.

The significantly positive fuel-efficiency aspects associated with concrete pavements also result in a reduction in the CO2, nitrogen oxides (NOx), and sulphur dioxide (SO2) emissions.

Emissions will be reduced by on average  532,160  lbs of C02, 6,025  lbs of NOx,  and 762  lbs of SO2 over the specified road design life.

The Bigger Picture

The example roadway you analyzed above is just one piece of the puzzle. Imagine the significant positive impact that could be made by considering the bigger picture, and employing green street strategies all across the U.S. The collective savings opportunities in energy, money and emissions are quite simply staggering. For example, if the 160,000 mile National Highway System were entirely made with a concrete surface (it is about 16%  now), it would result in a system-wide savings of 2.1 billion gallons of diesel fuel and a reduction of 15 million tons of CO2 per year.

Of course, these enormous savings do not even include the positive contributions that superior longevity, less maintenance or resurfacing, and lower energy demand for street lighting provide. Collectively, these benefits together make a clear case for embracing green (concrete) streets today.

References

·         Ardekani, S.A. and Sumitsawan P., "Effect of Pavement Type on Fuel Consumption and Emissions in City Driving."

·         Athena Institute, "A Lifecycle Perspective on Concrete and Asphalt Roadways: Embodied Primary Energy and Global Warming Potential."

·         Federal Highway Administration, "Development and Use of Price Adjustment Contract Provisions," T5080.3.

·         Taylor, G.W., and J.D. Patten, "Effects of Pavement Structure on Vehicle Fuel Consumption: Phase III," prepared for the Cement Association of Canada and Natural Resources Canada Action Plan 2000 on Climate Change, 2006.

·         QD009P, “For the Long Haul,” 2006.

·         QD023P, “Conserving Fuel in the Road,” 2007.

Additional Resources

·         SR385P, “Green Highways,” 2007.

·         QD025P-1, “Nall Avenue: A Green Street,” 2008.

·         QD020P-3, “Greener Highways: Interstate 80 near Salt Lake City, Utah,” 2007.


 
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American Concrete Pavement Association
5420 Old Orchard Rd., Skokie, IL 60077

Tel. 847.966.2272
E-mail: acpa@pavement.com