1. A general overview of pavement preservation and the role of Superpave/newer technologies in accomplishing that in a cost-effective (over time) manner.
=========================================================
Save the Road, Save Some Money
A crisis of road deterioration is challenging federal, state and local budgets. Better road preservation methods are being devised, fortunately, offering improved highway maintenance economics.
It’s pretty hard to tally the complete value of working highways and roads in America. The country’s approximately four million miles of pavement connect not only cities, towns and villages, but manufacturing plants, warehouses, freight stations and ports. Goods from abroad as well as USA-made products move around the country on rivers of asphalt, keeping our $200 trillion economy chugging along.
The six-day closure of the San Francisco Bay Bridge, in late October 2009, diverted 228,000 cars from their normal daily commute. As an alternative, a portion of the workforce remained functional by telecommuting. Some commuters drove north to the Golden Gate Bridge, while others south to the Haywood-San Mateo span – no doubt confounding motorists who routinely use those spans. BART, the Bay Area Rapid Transit system, reported its biggest day in history with 437,000 thousand taking the train one day of the shut down. Reportedly, no one was happy.
All this because of a broken cable that protected a cracked beam. Elsewhere, there are many, many more things that can get in the way of smooth transportation. Most dramatically, the collapse of Minneapolis’ I35W Bridge in 2007, where 13 people lost their lives (and the region reportedly lost $400,000 in commercial traffic every day), was due to a sudden infrastructure breakdown. But drive around almost any city in America, coast to coast, Canada to Mexico with Hawaii and Alaska counted as well, and you’re likely to see the bane of all driving: potholes.
Potholes have been around since the Romans were building roads all over their empire. But modern roads are getting worse lately: the U.S. federal highway system was initiated a little more than fifty years ago by the Eisenhower Administration and 46,876 miles of the Interstate Highway System were built over the next several decades, designed to last about fifty years. This is a ticking time bomb.
To put numbers to these worries, highway and transportation watchdog groups weigh in on what they see happening in road deterioration:
- TRIP, a national transportation research organization, claims that 23 percent of major U.S. metropolitan roads have pavements in poor condition. Included in this are interstates, freeways and important local roads.
- The Federal Highway Administration (FHWA) says that only half of these roads can be categorized as being in good condition.
- FHWA says that rural roads are in better condition, but still 39 percent fail to meet “good condition” ratings.
- FHWA says that 25 percent of urban roads – those that carry most of the nation’s traffic – are in poor condition.
- TRIP also reports that on average, urban motorists suffer $413 in additional vehicle operating costs resulting from increased fuel consumption, additional maintenance and vehicle deterioration due to rough pavement.
- The TRIP report also details city-by-city road deterioration statistics. Los Angeles has the dubious distinction of being the worst, with 64 percent of its major roads in poor condition. Almost as bad, in descending order, are San Francisco-Oakland (61 percent); Honolulu (61 percent); San Jose (60 percent); San Diego (53 percent); New Orleans (50 percent); New York City (49 percent); Sacramento (46 percent); Baltimore (42 percent); Oklahoma City (41 percent); Tulsa (40 percent); Albuquerque (39 percent); Omaha (38 percent); San Antonio (37 percent); Philadelphia (36 percent); Detroit (36 percent); Riverside-San Bernardino (35 percent); Oxnard-Ventura (35 percent); Houston (33 percent); Fresno (30 percent); and Washington, DC (30 percent).
FHWA attributes deteriorating roads to aging of pavement, unrelenting traffic and trucks carrying heavy loads of freight.
Road conditions actually improved from 2000 to 2006, but began to decline again in 2007. What happened? FHWA says this is due to under-funded maintenance and deferred new construction, all tied to tighter budgets.
Things were getting better, but …
Road conditions actually improved from 2000 to 2006, but began to decline again in 2007. What happened? FHWA says this is due to under-funded maintenance and deferred new construction, all tied to tighter budgets.
The troubling economics of deferred road repair today is that it increases costs tomorrow. According to an article in Better Roads magazine (March 2009), “A pothole is like a tooth cavity. Left untreated it gets more decayed, more painful, takes more time and money to care for, and sometimes you end up having to urgently call in a specialist.”
The pain (cost) happens in both micro and macro terms:
- The individual driver traversing a rough road will suffer vehicle damage, such as blown tires, cracked wheels and axels, and broken shock absorbers and struts, which dangerously alters steering and handling. That can be around $100 per tire and up to $500 per wheel if it is damaged also. TRIP reports that on average, American motorists shell out $335 in additional vehicle operating costs due to rough pavement, with drivers in several cities (Los Angeles, San Jose, San Francisco-Oakland and Tulsa) absorbing more than $700 per car in such repairs each year.
- Municipalities, states and the federal government pay more for replacing roads than if they instead maintain existing roads over time. The U.S. Department of Transportation/Federal Highway Administration, in its 2005 report At the Crossroads: Preserving Our Highway Investment, state clearly that “Higher quality investments earlier in the life of the road will save money over the long run because maintaining a road in good condition is less expensive than repairing or rebuilding one in poor condition.”
Yet the money runs short. The American Association of State Highway and Transportation Officials (AASHTO), in a joint report compiled with TRIP titled Rough Roads Ahead, Fix Them Now or Pay For Them Later, projects the national annual outlay for all capital investments in infrastructure, highways and bridges, should be $166 billion, each year through 2015. This far outstrips current spending, which in 2006 was only $78 billion.
In a recession, tax revenues naturally drop. Traffic does too, which reduces some road damage from cars and trucks. But rain, snow and freeze-thaw cycles continue unabated. Potholes are as certain as death and taxes.
Superpave technology to the rescue
Yankee ingenuity abhors a vacuum (and if you’ve driven around Boston lately, it is easy to see why). There are better roads ahead if we can just migrate to new methods and materials.
We’re already on our way there. A project authorized by Congress in the late 1980s, the Strategic Highway Research Program (SHRP), has successfully developed and evaluated technologies and techniques to combat the problems with our roads. Costs for the program were shared with state transportation departments, while the actual research was conducted under contract with universities and private companies.
SHRP studied asphalt, concrete, highway operations maintenance and safety and long-term pavement performance. More than 100 products were developed in the six years of the program, which have been showcased and shared with the highway building and maintenance community (including through the FHWA-sponsored National Asphalt Training Center, based in Lexington, Kentucky).
The highest-performing products to come out of this research are collectively known as the Superpave® program. This broadly is made up of three components: asphalt binder specifications, a design and analysis system that is based on volumetric properties of the asphalt mix, and models for mix-analysis tests and performance prediction. Of course part of the research outcomes were products that fit different climate and traffic conditions.
For example, in asphalt binders, the traditional material is a hot mix of petroleum joined with a specified grade of aggregate. Produced hot from the plant, it is put in trucks for use by road crews to either repave a road or fill in potholes. Because it has to be applied while still warm, all kinds of inefficiencies are intrinsic to its use.
Cold mix technologies, however, eliminate the logistics problems associated with hot mix applications. This frees up more road crews to actually fix potholes, for example, rather than wait in line at a processing plant for that day’s mix. When a truckload is half empty at the end of a day, it can simply be rolled to the next day. The material is adaptive to a broad range of temperatures.
Of greater importance is how Superpave products perform. One brand in wide distribution is EZ Street Cold Asphalt, which uses a low molecular weight liquid polymer modifier, also known as a reactive aggregate insertion polymer. It’s particularly good at resisting water, the enemy of all asphalt paving. Its adhesion and cohesion properties also contribute to its performance over time. Application of the mix requires no special equipment or methodologies, just a dump truck, plate compactor, asphalt rake and shovels. When necessary, it can be a throw-and-go process, pressed into water-filled potholes and driven on moments after installation.
The director of public works in Millersville, Tennessee remarked in Tennessee Public Works (January/February 2002) that EZ Street enabled his crews to work with greater efficiency in patching potholes than with hot mix, and that it held up to traffic ten to 12 longer than traditional hot mix. The mix also cut down his labor needs considerably.
The Texas Transportation Institute (TTI) has conducted macroeconomic analysis of the benefits of SHRP products and Superpave technologies. Very conservative estimates on service life extensions of roadways project a $1.3 billion to $2.1 billion in savings per year to motorists in reduced auto maintenance, wear and tear, plus a reduction in highway agency costs that range from $484 million to $785 million annually.
Superpave methods and materials generally cost more upfront, which makes them difficult to rationalize in a tight economy. But American commerce and culture show no sign of reducing their dependence on roads, telling us these new and improved methods can’t come into use soon enough.
