Unpaving Some Roads

SUBHEAD: In the future we will not be able to afford the maintenance cost and material for asphalt roads.

By Staff on 12 April 2016 for Energy Skeptic -

Image above: A badly paved Meadow Lake Road, right before the entrance to the Grand Central Parkway in Queens, New York in 2009. This road should be repaved or abandoned. From (http://queenscrap.blogspot.com/2009_06_01_archive.html).

The U.S. has 4.1 million miles of roads (1.9 million paved, 2.2 million gravel). About 3 million miles of roads have less than 2,000 vehicles a day, less than 15% of all traffic. The paved portion of these low-volume roads ought to be evaluated for their potential to be unpaved.

Many of these roads should have never been paved to begin with, but the costs of construction, asphalt, and energy were so cheap it was done anyway.  Now many rural roads are past their design life and rapidly deteriorating.  It is both difficult and expensive to maintain them, and dangerous to let these roads fall apart and degrade into gravel on their own.

Unpaving low-volume roads saves energy and money. According to Karim Ahmed Abdel-Warith at Purdue University, preserving low-volume roads costs several hundred million dollars a year, more than half of the annual investment in roads.

Unpaving would also slow vehicle speeds down, further increasing miles per gallon from less aerodynamic drag.

Since roads harm biodiversity, getting rid of a road entirely should be done when possible.
The NRC paper I’ve taken excerpts from below requested feedback from the 27 states that have already depaved roads. This report provides many helpful guidance documents on depaving roads for communities interested in pursuing this.

The historic trend has been to pave roads, not unpave them.   These policies arose in the last century when the costs of asphalt, fuel, and all construction expenditures were low compared with current costs and the axle loads carried on rural low-volume roads were significantly lighter than current loads.

The rising cost of asphalt and fuel and a significant increase in traffic and traffic loads on low-volume rural roads due to commercial, agricultural, and energy trucks, combined with stagnant or decreasing budgets, are causing a situation in which the cost of rehabilitating and maintaining very low-volume paved roads on the existing road network often is no longer feasible.

This study found that the practice of converting paved roads to unpaved is relatively widespread; recent road conversion projects were identified in 27 states on mainly rural, low-volume roads that were paved when asphalt and construction prices were low.

Those asphalt roads have now aged well beyond their design service life, are rapidly deteriorating, and are both difficult and expensive to maintain. Instead, many local road agencies are converting these deteriorated paved roads to unpaved as a more sustainable solution.

Many local road agencies reported cost savings after converting, compared with the costs of continuing maintenance of the deteriorating paved road, or repaving.

Low-volume, rural roads serve as main routes for numerous industries, farmers, and ranchers to get raw material from source to distribution or processing centers, provide ingress to remote public lands, and act as transportation arteries for millions of rural residents. Most of these rural roads have low or very low traffic volumes and have unpaved, aggregate surfaces. Historically, unpaved roads have been considered the lowest level of service provided.

In a demonstration of progress and an effort to improve road conditions for rural residents, many agencies paved low-volume roads with little or no base preparation when asphalt and construction prices were low. Those asphalt roads have now aged well beyond their design service life, are rapidly deteriorating, and are difficult and expensive to maintain.

The increasing sizes of agricultural and commercial equipment, including that used by the energy sector, are compounding road deterioration in many areas.

Traditionally, these roads were maintained or repaved at regular intervals, but with the increasing traffic loads, increasing cost of materials, and stagnant or declining road maintenance budgets, many agencies do not have the funding to support these activities.

Instead, many local road agencies are looking to convert deteriorated paved roads to unpaved ones as a more sustainable solution.

The state of the practice for converting roads from paved to unpaved involves reclaiming or recycling the deteriorated pavement surface, supplementing existing materials as needed, compacting, and for some applying or incorporating a surface treatment, such as a soil stabilizer or dust-abatement product.

In a few cases, no recycling of the old pavement was done, and new surface aggregate was simply placed over the deteriorated road surface.

However, most agencies that have done conversions recycle the old surface in-place and reshape and compact it as a base for a new aggregate surfacing. Thereafter, the new surfacing ranges from locally available gravel to high-quality surface aggregate that can be maintained with motor graders to sustain adequate crown and a smooth surface.

Many of the roads that have been converted from paved to unpaved had annual average daily traffic (AADT) of between 21 and 100 vehicles, suggesting that many of the roads that are being converted should not have been paved initially or that road usage patterns have changed significantly since paving.

Local road agencies are converting roads primarily as a result of a lack of funding for maintenance and construction, safety issues, and/or complaints from the public. Road budgets have remained stagnant or declined in recent decades, but the costs of labor, materials, and equipment have continued to increase. Consequently, local road agencies have been left underfunded and are struggling to maintain their existing road network. Limited maintenance of deteriorating roads (e.g., pothole patching) often is all that can be done with existing resources, with repaving often being cost-prohibitive.

The reported cost of converting ranged from $1,000 to $100,000 per road segment or mile within the United States and Canada. The variation in costs is attributed to how costs are tracked by agencies, how the conversion was done, equipment requirements, supplemental materials, surface stabilization and dust abatement, and addressing drainage and road base issues.

NEEDED: Unpaving guides
A significant lack of available resources, such as a handbook or design guide, for practitioners who are considering or performing road conversions was noted. Numerous survey respondents indicated that they did not use any documented resources when planning and performing the conversion and often used a trial-and-error approach.

In addition, road agencies rarely document procedures and outcomes of road conversions, such as construction problems, crash rates, public concerns and reaction, and comparative maintenance costs of the new surface.

Completing successful conversions is possible with appropriate investigation and design, selection of quality granular surfacing materials, and good construction, and by involving and educating the public as part of the process. However, limited information has been published to guide practitioners in these processes.

There are more than 4.1 million mi of roadways in the United States. There is no uniform agreement on how many of these are low-volume roads. About 53% are unpaved and are maintained by local and state transportation departments.

Unpaved roads are nearly always considered low volume.
For the purpose of this project, low-volume or very low-volume roads are defined as roads with AADT of less than 250 vehicles, based on research that determined that converting paved roads to unpaved was cost-effective at this threshold.

The spectrum of options of surface types for low-volume roads ranges from gravel with no treatment to stabilized gravel to bituminous sealed bases to asphalt and concrete pavements. Each road surface type has its own merits and represents one tool in the road management toolbox.

Unpaved roads can be defined as those with a surface course of unbound aggregate (gravel) where no binder, such as tar, bitumen, cement, lime, or other chemical additive, is used. An unpaved road often requires blading at least once annually to maintain the road surface in a drivable and safe condition.

Paved roads are defined as those with an asphalt concrete or portland cement concrete surface, or roads that possess any combination of asphalt binder and aggregate intended to provide waterproofing, adhesion, structural strength, and frictional resistance.


Active versus Passive Conversion
Many transportation agencies facing budget shortfalls and deteriorating paved roads are converting their paved roads to gravel (active conversion), whereas other agencies are allowing roads to deteriorate to unpaved conditions owing to a lack of funding for maintenance (passive conversion).

Active conversion is the process of converting a paved road to an unpaved road using equipment and personnel to recycle the old pavement into a pulverized material that can be used as a base for a new aggregate surfacing or as part of the new surface. Passive conversion of a road from paved to unpaved is the natural process of the paved road breaking down and deteriorating to an unpaved surface as a result of exposure to the elements and wear and tear from vehicle traffic.

Based on survey and interview responses, active conversion is a far more common practice, however some local road agencies find that passive conversion occurs simply as a result of a lack of funding for properly maintaining roads.

Factors to Consider for Unpaving
  • Road condition: This dictates whether a deteriorated paved surface can be economically repaired to restore it to an acceptable condition or whether there is a need for complete rehabilitation or reconstruction, which may not be affordable. In the latter instance, conversion to gravel can be considered.
  • Safety: The deterioration of a paved road surface may be such that it may be safer to convert to a gravel surface either permanently or for an interim period until the road can be rehabilitated or reconstructed.
  • Presence of heavy and overweight vehicles: A high volume of heavy vehicles has a significant impact on the standard required for pavement maintenance and rehabilitation. Initial costs to repave or repair a road to an appropriate standard for these vehicles may be unaffordable for achieving an acceptable life cycle. Gravel roads can be much cheaper to repair when damaged, but the frequency of repair may be greater.
  • Maintenance capability: Specific equipment and skills are required for paved and unpaved road construction and maintenance. The availability and affordability of either contracted or in-house equipment or skill need to be assessed to compare the ability to maintain each surface type effectively. Dust and erosion control may be a significant factor and could be considered for unpaved surfaces.
  • Environmental issues: Air and water quality impacts from dust and erosion can affect human, plant, animal, and aquatic health and create a safety hazard to drivers. Products used to stabilize the road surface and reduce dust can also affect the adjacent environment if incorrectly selected or applied.
  • Dust and erosion control: These issues may or may not be a significant factor, but it is essential that they be considered for all surfaces.
  • Availability and quality of suitable unpaved road–wearing coarse aggregate sources: The quality and properties of the aggregate have a significant impact on the surface condition and frequency of maintenance required on unpaved road surfaces. Appropriate unpaved road surfacing aggregates are not offered by many commercial aggregate suppliers and can be expensive or difficult to obtain. This issue is more important than many managers recognize.
  • Network significance of the road: Primary routes that are frequently used by public transport (including school buses) or emergency vehicles or are priority snowplow routes generally are not recommended for conversion from paved to unpaved surfaces. Local roads serving limited access to residences or businesses are better candidates.
Changes in Traffic Patterns and Vehicle Type
Modern agricultural equipment (i.e., tractors, combines, farm trucks) have greatly increased in size and carrying capacity, along with greater crop yields, creating increased maintenance issues on paved and unpaved rural roads (Anderson 2011), with accelerated degradation of low-volume roads (Figure 6). Multiaxle semis, concrete haulers, large-load log trucks, and rising traffic volume can be equally destructive (Etter 2010; Taylor 2010) (Figure 7).

In some areas of the country where oil drilling and extraction have increased, such as North Dakota, Texas, and Pennsylvania, significant damage to roads from oil field traffic has occurred (Floyd 2013). Many of these rural paved roads have passed the end of their design life (Anderson 2011).

The 2010 Wall Street Journal article “Roads to Ruin: Towns Rip Up the Pavement” highlighted the economic strain many counties face when trying to maintain paved roads in rural areas (Etter 2010).

A recent study found that the state of Iowa would need to increase road funding by $220 million annually just to maintain the current road network (Anderson 2011).

Similar funding shortfalls for local road maintenance budgets are occurring across the country (Canfield 2009; Taylor 2010; Landers 2011). Cold-weather states in particular have high maintenance costs resulting from the repair of damage caused by freeze-thaw cycles but little available funding because of essential winter maintenance operations (Canfield 2009).

Coupled with declining budgets, agencies have seen raw material prices increase. Costs for gasoline, diesel, and asphalt binder, all petroleum-based products, are tied to fluctuating oil prices (Taylor 2010). However, fuel taxes, which are a primary source of funding for road maintenance, have remained constant in this time period. Improved fuel consumption technologies have further reduced this source of income.

The recent economic downturn has made governments reluctant to increase other taxes and has resulted in people driving less.


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