Major Issues And Trade-Offs For Improving Pavement Sustainability Through Design
The major design and policy objectives, associated approaches to providing sustainability improvements, and potential trade-offs with regard to economic, environmental, and societal impacts are summarized in table 1. See Chapter 4 (.pdf) of the Reference Document for more details.
| Design/Policy Objective | Sustainability Improving Approach | Economic Impact | Environmental Impact | Societal Impact |
|---|---|---|---|---|
| Achieve Longer Life | Use ME design to be able to consider alternative materials, construction specifications and structures to increase life for same pavement thickness1, 2. Use selected recycled materials to improve structural characteristics. Require higher construction quality. | Virgin materials may increase cost; increased construction quality may increase cost; reduced frequency of maintenance and postponement of rehabilitation may decrease cost. | Virgin materials may have higher environmental impact during production; decreased maintenance frequency may decrease emissions; increased pavement quality may decrease user emissions. | Stays smoother longer; less delay associated with maintenance. |
| Achieve Longer Life | Use of higher quality materials. | Increased cost of materials; decreased cost of maintenance. | Potential for increased emissions due to production and transportation of higher quality materials if not locally available; higher quality pavement may result in lower user and maintenance emissions. | Higher quality pavement; less delay associated with maintenance. |
| Achieve Longer Life | Improved construction specifications (less variability, greater density, stiffness, strength, durability depending on material)2. | Somewhat increased initial cost; could decrease maintenance cost or upfront cost if reduced thickness is used. | Less frequent maintenance or reduced thickness will reduce environmental effects of construction and materials use; additional initial construction work may have minor impact. | Less delay associated with decreased maintenance. |
| Consider Inlaying New Truck Lane Pavements (vs. Multi-lane Overlay) | Minimize total material used for rehabilitation by not overlaying lanes to match grade that do not have structural needs. | Can reduce cost; may cause some additional traffic delay. | May reduce total amount of new materials needed; can consider recycling materials removed from old truck lanes. | May cause more initial traffic delay due to closure for reconstruction. |
| Obtain Same Life for Reduced Thickness | Use ME design to consider new materials, construction specifications, pavement structure types1, 2. | Virgin materials may have higher cost; increased construction quality may increase cost. | Potential increase due to production of virgin material; less material use lowers environmental impact due to reduction in production, transportation and construction. | May reduce traffic delay due to more rapid construction. |
| Reduce Noise Emissions | Use of noise reducing asphalt (open-graded) or concrete (new generation concrete surfaces) surfaces.3 | Increased cost; more frequent replacement for the asphalt surface. | Minor impact of additional grinding/grooving for concrete; more materials use and construction. | Reduction of noise in surrounding areas. |
| Achieve/ Maintain Pavement Smoothness | Consider smoothness over the pavement life as a key design parameter, especially for high traffic volume routes. Include construction specifications for smoothness, design features to maintain smoothness, and costing of maintenance to keep surface smooth. | Potential for small to moderate increases in initial costs but reduced life-cycle costs due to longer pavement lives. Reduced vehicle operating costs for road users. | Reduced environmental impact due to less fuel use, particularly on high traffic volume routes. | Improved economic efficiency. |
| Maximize Use of Recycled and Local Materials | Use recycled pavement materials to replace virgin materials and minimize transportation distances for materials.1 | Higher variability in recycled material quality may increase maintenance frequency and life-cycle cost; generally reduces initial cost. | Reduced impact of materials production and transportation; less use of scarce materials; use of stabilizers have an impact and can be compared with benefits of reduced need for resurfacing layers, transportation of materials, etc. | May increase maintenance delay if materials do not perform as expected in design; reduced landfill disposals. |
| Maximize Use of Recycled Material | Use recycled materials from other industries to replace virgin materials.1 | Use where transportation cost feasible if not locally available; Evaluate variability in material quality to avoid increase maintenance and rehabilitation; generally reduces initial cost;additional processing orconstruction issues may increase initial cost. | Use where transportation and processing are environmentally beneficial; may reduce future recycling if inclusion of recycled materials makes future recycling too costly, unpredictable or difficult; reduced impact of virgin materials production; less use of scarce materials. | May increase maintenance delay if materials do not perform as expected in design; reduced landfill disposals. |
| Minimize Impact of Utility Construction | Eliminate or minimize utility cuts in pavement, or use pavement systems that allow easy restoration of pavement structure after utility work (utility corridors in pavement). | Higher initial cost; reduced life-cycle costs due to less frequent maintenance and rehabilitation; reduced cost of maintenance and rehabilitation with no manhole covers; reduced life-cycle cost if longer life designs are used. | Potential increased initial materials and construction impacts of utility corridor; reduced impacts due to longer pavement life, less frequent maintenance and rehabilitation. Keeping utilities out of pavement improves ability to do in-place recycling strategies. | Smoother pavement over life cycle; increased pavement life resulting from less frequent repairs and patching. Keeping utilities out of pavement improves ability to do in-place recycling strategies. |
| Minimize Impact of Construction | Accelerated construction. | Often reduces initial user costs but increases agency costs; must maintain quality standards. | Difficulty with shorter construction may influence quality and functional life; accelerated materials may have a shorter performance life. | Reduced traffic delay. |
| Use Pavement to Capture Runoff Pollutants and Reduce Hydraulic Requirements from Storms3 | Use partially permeable pavement (e.g., open-graded asphalt). | Increased cost; need for more frequent resurfacing. | Increased environmental impact of materials and construction for open-graded layers; reduced pollutants in water. | Cleaner water for surrounding area. |
| Use Pavement to Capture Runoff Pollutants and Reduce Hydraulic Requirements from Storms3 | Use fully permeable concrete or asphalt pavement (very little application to date, only for highway shoulders). | Largely unknown; increased cost, need for more resurfacing; potential to reduce stormwater conveyance. | Requires more materials, thicker layers than conventional shoulders; reduced pollutants in water; groundwater recharge. | Cleaner water for surrounding area. |
| Use and Maintain Pavements that Reduce Urban Heat Island Effects and Reduce Lighting Costs where Warranted by Net Benefits | Where it is determined to be beneficial based on assessment of the life cycle for specific project type and climate region, engineer pavement to reduce heat island effects.3 | Range of potential costs from net reduction to neutral to net increase if energy savings from air conditioning and lighting are less than pavement alternative life-cycle cost differences. | Increased impact of thickness and materials if not warranted by climate, urban environment, lighting requirements; potential for increased environmental impact of materials designed for thermal characteristics; reduced energy use due to less required lighting. | Less energy use from air conditioning in locations where pavements make substantial contribution to increased urban temperatures in late afternoon and evening. |
| In Future, Consider Fuel Use Due to Structural Responsiveness to Vehicle Loading | Once calibrated models are available, consider using them to determine where structural responsiveness is significant and develop appropriate strategies based on those results.3 | Calibrated models will permit evaluation of alternative structures considering traffic, climate and other variables which will allow consideration of both road user and agency costs versus environmental benefits for designs. | Optimization may reduce environmental impact due to less fuel use, particularly on high truck traffic volume routes. | Optimization may improve economic efficiency particularly on high truck traffic volume routes. |
Note: For more details on:
1Materials, including recycled materials, see Chapter 3 (.pdf) of the Reference Document
2Construction quality, see Chapter 5 (.pdf) of the Reference Document
3Use-phase considerations, see Chapter 6 (.pdf) of the Reference Document
4Maintenance and preservation, see Chapter 7 (.pdf) of the Reference Document
5Interaction of cost and sustainability, see Chapter 10 (.pdf) of the Reference Document