The growing population of the world's cities is creating a large demand for roads and highways. These roadways must be designed to serve transportation, ecosystems, urban growth and public health.
The University of Washington's Civil & Environmental Engineering Department is advancing the development of green roads through a new rating system called "Greenroads." This system awards credits similar to those awarded by LEED for buildings.
Reduced Carbon Dioxide Emissions
The transportation sector is the largest source of carbon dioxide emissions in the world. Each gallon of gasoline creates about 20 pounds of CO2 and a single passenger car, pickup truck or minivan emits around half of that amount.
But reducing your carbon footprint does not have to be impossible. Some of the most effective ways to reduce your impact are to walk, bike and use public transport.
Travelling on an electric or hydrogen-powered bus emits a fraction of the greenhouse gases of taking a private car, and is becoming increasingly popular in cities worldwide. A taxi or ride hailing app also emits a lot of climate pollution, but pooling rides, choosing an electric vehicle or using it to connect with public transport all have the potential to significantly reduce your emissions.
Reduced Soil Erosion
When heavy rain falls, tonnes of soil can be eroded from fields and farmland. This can lead to flash floods and land damage downslope.
However, it is possible to reduce soil erosion by introducing green vegetation. Trees are a great way to do this because their leaves slow down and divert water before it reaches the ground.
The study found that the largest reduction of soil erosion occurred in areas that were 0-1 km away from roads. The mean annual soil erosion rate was reduced by more than 589 t*km-2*a-1 in these buffer strips.
Increased Water Retention
Green infrastructure prevents runoff by capturing rain where it falls, allowing it to filter into the soil or return to the atmosphere through evapotranspiration. It also limits the volume of water required to treat sewer systems and sewage, which reduces costs.
Moreover, it reduces the amount of salt that is needed to keep roads clean. Salt-laden stormwater carries chloride and sodium into major bodies of water, negatively impacting marine life.
Green streets also limit the formation of potholes by keeping asphalt at low temperatures and preventing ice production. In addition, they improve air quality, increase safety for pedestrians and bicyclists, and make neighborhoods more attractive.
Reduced Noise Pollution
Noise pollution is an important problem for urban areas. It has been linked to a number of negative health effects, including annoyance and sleep disturbance.
Road traffic noise is the most common type of noise pollution in urban areas and accounts for 80% of all communal noise sources. It is responsible for a large portion of traffic-related air pollution, as well as causing significant damage to human and animal health.
Residential green and availability of neighbourhood green spaces have been associated with reduced transportation noise annoyance in various studies. The effect of residential green on noise annoyance was investigated separately for road, railway and aircraft noise.
Increased Wildlife Habitat
Wildlife-friendly road crossings and habitat corridors can help reconnect wildlands that have become fragmented by extensive highway systems. They are proven to reduce wildlife-vehicle collisions, sometimes by 80-90%, improve landscape connectivity, and save lives and money.
A key aspect of these strategies is understanding animal preferences and habitat needs. A number of states have undertaken studies on this issue, and Pew has helped lead a series of workshops that bring transportation agencies, wildlife managers, nongovernmental organizations, property owners, and tribal members together to identify gaps in knowledge and build partnerships for safe-passage projects.
A recent effort in Vermont, led by Scott and Susan Morse, founder of Keeping Track, and research herpetologist Jim Andrews from Middlebury College, is training transportation staff about the needs of local wildlife species. The 8-day course includes classroom lectures and field visits.
