The buzz of innovative ideas on how to build cheaper, greener roads is all around us. These ideas range from using scrap construction materials and rubber tires to using recycled glass to reduce our reliance on asphalt. While these brainstorms are laudable, they’ve yet to prove themselves in a total life-cycle analysis.
The green construction practices that have a demonstrated track record can’t gain traction because of an archaic contractor bidding process. And herein lies the problem. A problem that we can no longer afford to ignore given the sheer cost and impact of our highway system.
“Our roads are everywhere. Anywhere you turn, you’re automatically on a road. We can’t get away from them. We step outside of our house and we’re on a road. If we go to a National Park, we take a road. People don’t realize this but [building roads] is one of the highest impact things we do.” – Shane Stathert, Think Green Roads
The need for lower impact roads is a pressing economic issue. Each year, we spend roughly 7 percent of our Gross Domestic Product (GDP) on transportation infrastructure. For fiscal year 2010, that amounted to nearly $1 trillion. A key input to these costs is the amount of asphalt we use. But the costs don’t end there.
A typical two-lane mile stretch of highway uses roughly 25,000 tons of crushed stone, which is what makes aggregate (the base layer for roads) one of the most mined materials in the world. Then there’s the CO2 emissions. The 32,300 lane miles of road the United States paves every year emits millions of tons of CO2. Here’s a conservative estimate.
Constructing a single-lane mile of road emits 1,200 tons of CO2. If we assume every mile of road built is single-laned (yeah right, not in America) then building our roads emits 38,760,000 tons of CO2 every year. That’s the same as the annual energy use of 6 million homes. Seriously, 6 million, stop and think about that for a second.
Needless to say, these exorbitant costs – both fiscal and environmental – left many in the industry wondering: how can we reduce expense and still maintain the quality of road construction? Thus, the green road construction movement was born.
Recycled Materials: A Reliable Aggregate Alternative?
With 94 percent of paved roads covered in asphalt, the first obvious target was determining how excessive use of asphalt could be reduced to minimize economic and environmental impacts. One idea that’s gaining a lot of attention in the green construction movement is the use of recycled materials for aggregate.
The logic is simple: pick a material with a good consistency that would normally sit in a landfill, grind it up and you’ve got an aggregate substitute or aggregate base. Popular fillers and aggregate replacements include rubber tires, roofing shingles and even glass.
Using recycled material for aggregate in this way not only saves money, but it also makes use of a material that would otherwise remain unused. A single lane mile of road constructed with rubber tires will use roughly 2,000 tires and save as much as $50,000. It also diverts rubber tires from landfills where they’d otherwise pile up and present a fire hazard or act as a breeding ground for disease-carrying mosquitoes.
But putting what would otherwise be considered trash into our roads raises a healthy amount of skepticism. What happens when the roads break apart? Is it safe for plastics, rubber and used construction material to be exposed to the elements? What if these wash into our water system?
There is a dearth of research on the environmental costs of using such recycled materials for aggregate or mixing them with asphalt. And using recycled rubber is one of the most promoted ways to green a road today. Both the Green Highway Partnership and National Asphalt Association tout recycled rubber as an environmentally safe and viable alternative.
Because there are few total life-cycle cost analyses available, it will be at least a generation before we know the true impacts of these methods. And while it remains to be seen how these recycled materials measure up as safe alternatives, there’s another, more pressing, issue blocking green road construction: cost-plus contract pricing.
Cost-plus Contract Pricing Is Blocking Green Roads
Even though the case for environmentally sound construction practices is growing, there continues to be a major hiccup in the road: contractors. More specifically, the agreements contractors use, known as "cost-plus pricing," are slowing things down. That’s because in the current road construction bidding structure, there’s a benefit for contractors using excess asphalt and man hours. Thus, there’s less incentive to explore greener methods of road construction.
The contractual stipulation of cost-plus pricing is in place throughout North America (with the exception of North Carolina). The way it works is this: requests for proposals (RFPs) – requests for contractors to bid on a job – typically go out in the fall. By winter, contracts are awarded to the various contractors that win their bids. For the remainder of the year, projects are in process until their completion.
"Once we’ve already extracted the materials, we should be doing everything we can to recycle them in place to minimize the demand and future extraction of oil. Forget about the environment for a second, this is straight economics." – Shane Stathert
Cost-plus pricing was developed to control the variable cost of bitumen involved in the bidding process. Bitumen is the key ingredient of asphalt. Because it’s closely linked to the price of oil, there is a lot of price fluctuation. To safeguard against price peaks and valleys, contractors created a cost-plus pricing stipulation in their bids.
This means that contractors are paid for the cost of their labor plus the cost of the asphalt. So, if a contractor uses more asphalt on a project, they’ll make more money. Since roads are funded from the public coffers, the taxpayers are the ones getting steamrolled. In a system that rewards waste at a fundamental level, green road construction is stuck at an impasse.
Three Green Techniques That Aren’t Given A Chance
There are three common methods of recycling asphalt and using green methods in road construction. Each of them could vastly improve the road construction process if they were given the chance to flourish. However, cost-plus contracting effectively diminishes the use of these techniques. Here’s a brief overview of the types of on-site road recycling that need more support.
|Hot in-place recycling||Used when the road needs to be resurfaced and there is no structural damage. Asphalt is heated on-site, saving energy and emissions.|
|Cold in-place recycling||Used when the road needs to be resurfaced and heat is not required. Instead the asphalt is mixed with emulsion to limit fumes and energy use.|
|Full-depth reclamation (FDR)||Used when the road has structural damage and needs repair. Asphalt and foundation are ground together and then reused.|
Of the three approaches to road recycling, the hot in-place method has the most research behind it. Hadi Dowlatabadi, an environmental scientist at the University of British Columbia, conducted an in-depth study of the hot in-place road recycling method as part of a carbon credits project. In analyzing the environmental and economic benefits, Dowlatabadi found that hot in-place recycling reduces material use by 80 percent and material transport by even more than 80 percent.
Greenhouse emissions and energy use is also minimized. Compared to traditional paving methods, energy use is reduced by 50 percent. At the same time, greenhouse gas emissions are 60 percent lower. With these types of results, you’d think this would be the preferred method of highway construction, right? Right.
North Carolina Sets Standard for Low-cost Green Roads
The lone region that’s scrapped “cost-plus” contracting, North Carolina, is indicative of the untapped potential of green construction. Instead of awarding contractors on a cost-plus basis, North Carolina has established road performance criteria. That means contractors in North Carolina have to bear the cost of asphalt themselves and can use any method available to them as long as they meet the standards set forth by the engineer.
“What [we] need to do is say, ‘Roads need to be paved to this standard, give me the least cost contract.’ Let the contractor take up the risk of the asphalt. If they think they can do it and meet the standard through hot in-place recycling, they’ll do it. They may make more profits in the process, but that is what you want – you want to incentivize more sustainable roads.” – Hadi Dowlatabadi
And guess, what? North Carolina has the lowest cost of road construction in all of North America. Coincidentally, it’s also home to the highest amount of hot in-place recycling. Consider this, in British Columbia it costs $25/square meter to build a road; in North Carolina it costs roughly $19/square meter. It’s no surprise that these lower costs result in higher profits without the need to use more asphalt.
Go Green to Improve Roads & Save Money
In addition to reducing the cost of road construction, incentivizing green construction techniques will help us maintain higher quality roads. With road construction costing less, we’ll be able to repair more of our aging infrastructure. And improving the road conditions has far reaching impacts: it will reduce greenhouse gas emission and, more importantly, it will help save lives.
Studies have shown that poor road conditions account for roughly 10 percent of our greenhouse gas emissions for traffic. Simply improving the conditions of our roads could have a massive ripple effect – not to mention provide an opportunity to reduce the environmental and economic impact from of road construction cradle to grave.
On a more important note, improving the conditions of our roads will reduce the number of car-related fatalities. The National Highway Traffic Safety Administration estimates that roughly one out of three car related fatalities is the result of poor road conditions. Improving the conditions of our highway system could save thousands of lives every year.
Clearly, promoting and rewarding green road construction is in the public’s interest. We just need to get out of the way and make it a reality. Have any thoughts on how we can make it happen? Leave me a comment below.
Thumbnail image created by Zahlm.