The United States highway system puts Roman roads to shame as the largest public works project in the history of man. With an approximate cost of $425 billion, the government's reluctance to abandon the network of roads and highways that provide low cost per capita transportation to the country is completely understandable. Although mass transit is demonstrably more sustainable than the continued reliance on motor vehicles as the primary means of transportation, a complete and immediate shift to buses and trains is not only logistically impossible but also culturally infeasible.
Simply put, people are going to keep driving cars, which means we'll always need roads. Recognizing this fact, a growing group of advocates has chosen to address the negative environmental impact of poorly planned roads by suggesting the adoption of a road rating system similar to the system LEED (Leaders in Energy and Environmental Design) uses for buildings. Though buildings only have a point source impact, and roads have both the point source impact and a linear effect (since roads run through the landscape), the principles are essentially the same. By using preset categories to award points for sustainable design, programs like Greenroads (Washington) can provide a system for incentivizing sustainable design. In addition, by defining and classifying elements for benchmarking, incentives can be structured to promote environmentally sound solutions. Finally, establishing reputable metrics for comparison will facilitate endorsement of sustainable projects over those without low impact elements of design.
For a road rating system to work effectively, the grading categories will have to be well defined, understandable to the public, and be irrefutably beneficial in terms of sustainability. Martina Soderfund, whose thesis paper sparked the Greenroadsproject, suggests six categories for a proposed rating system:
1. Sustainable Alignment
For most roads, cost of construction is the highest priority determinate of path. However, including this category in the consideration of sustainability ratings would add additional points for roads that avoided certain habitat types, such as wetlands, forests, farmlands, or other ecologically sensitive areas.
2. Materials and Resources
Asphalt, gravel, and tar have a high environmental footprint due to extraction, transportation, and use. The materials and resources category would reward projects that made efforts to reduce these impacts.
3. Stormwater Management
Seldom recognized by the general public, the continually increasing percentage of impervious land cover has negative implications for stormwater runoff and management. Promoting stormwater quality and quantity control through this category increases awareness of road impact and encourages the use of pervious surfaces.
4. Energy and Environmental Control
This category addresses some of the more subtle and inherent effects of typical roadway design. It evaluates the quality of design, while considering effects on light pollution, the heat island effect, quieter pavements, eco-viaducts (wildlife and fauna crossings), visual quality, and pedestrian/bicyclist access.
5. Construction Activities
The temporary activities of the roadway construction are a major source of pollution, waste, energy use, and health issues. Major concerns of this section can be categorized as: site disturbance, waste materials generation, noise pollution, emissions & energy usage, and the health of workers.
6. Innovation and Design
The credit definition of the last section is awarded for additional performance above the requirements set in the previous sections. Consider it extra credit or bonus points for exceptional performance in a particular category.