Skip Top Navigation

Health and Environment

Sky, mountains. land and body of water

Transportation systems touch many complex health and environmental concerns, including human health, natural ecosystem processes, species protection, climate change, and land use.

WSDOT’s environmental enhancement efforts take their cues from citizen expectations that have been captured over time in federal, state, and local environmental regulations and policies. Public discussion of emerging issues, advances in scientific knowledge, and the evolution of transportation practices further direct our efforts.

WSDOT’s overarching transportation goal related to human health is improving the safety of users of the transportation system. Beyond that core principle, WSDOT recognizes its role in protecting and sustaining the natural environment and the cultural and historic resources that are also critical to our quality of life.

The Health and Environment paper explores five ways that transportation systems interact with communities and the environment:

• Air quality

• Active living and healthy communities

• Noise issues for highways and ferries

• Stormwater runoff

• Protecting and connecting habitat

An analysis of growth management trends and policy recommendations will be released as a stand-alone paper later.

Protecting Washington’s water supply, air quality, natural ecosystems along with other efforts to sustain the abundant natural setting of this state is no small task and will require the efforts of every citizen. For a fuller description of WSDOT’s environmental work, visit the Environmental Services Website.


Environmental & Health Trends in Washington

Air Quality

Emissions associated with transportation – from cars, trucks, buses, cargo vessels, cruise ships, ferries, and trains – are major sources of local air pollution and greenhouse gases. Air quality trends for regulated pollutants have improved over the past few decades, even as the state’s population and vehicle miles traveled have increased.

However, concerns are growing in the areas of unregulated air toxics and inhalable soot (PM2.5) related to diesel exhaust. While scientific study of the health effects of diesel continues to evolve, it is generally understood that prolonged exposure to these fine particles lead to respiratory and other health problems. Steps already taken in the regulatory arena (low sulfur diesel fuel and new exhaust systems in heavy trucks) and in Washington State (the recent move to low sulfur diesel in all state ferries) have helped to reduce PM2.5 emissions by more than 20 percent from 1980.

Another emerging trend is the share of carbon dioxide (CO2) produced by transportation sector. Because Washingtonians rely less on fossil fuel for electricity generation, our vehicles are the largest source of CO2 emissions.

The opportunities to constrain CO2 emissions from motor vehicles lie in:

• Increasing fuel efficiency

• Converting to less polluting technologies

• Holding down vehicle miles traveled

WSDOT and other state and federal agencies are working together to respond to these issues.

Healthy Communities

Transportation not only determines how we move from place to place, but also the character of our communities. There is an increasing body of research suggesting that automobile oriented land uses (e.g., those that create auto dependency) limit transportation options, adversely affect air quality, water quality and safety, and discourage physical activity.

Some of the most compelling new research related to transportation and healthy communities has shown that:

• Children’s walking trips to school have declined by 40 percent between 1977 and 1999, and children between the ages of 5 and 15 make only 10 to 12 percent of their school trips by walking or riding their bicycles.

• Nearly a third of our nation’s children and adolescents are overweight or at risk of becoming overweight. This proportion has more than doubled over the past 20 years.

• One half of all trips people make are less than three miles, but most of these are made by car.

• People walking and biking on the road face disproportionately high risks as 13 percent of all traffic deaths are pedestrians.

Access to sidewalks and bike paths as well as transit friendly land use patterns can improve our health and the health of our communities by helping to improve air quality and providing more opportunity for physical activity.

Reducing Highway Noise

Traffic can create a lot of noise, sometimes at levels that are unacceptable for nearby neighborhoods. Though WSDOT cannot provide sound barriers everywhere, federal law and state policy requires that every project that adds through lanes or significantly realigns roadways must receive a noise evaluation. Outdoor noise impacts (more than 66 decibels) on locations such as homes, schools, churches, day cares, and hospitals trigger evaluation of whether noise mitigation (e.g., walls, earth berms) will be meaningful and cost-effective. The result is that WSDOT builds many noise barriers that generally halve residents’ perception of traffic noise. From 1963 to 2000, WSDOT built approximately 65 miles of noise barriers throughout the state.

Before 1976, noise was not accounted for on highway projects. WSDOT’s noise retrofit program allows placement of barriers on existing highways where homes existed before May 1976. More than seventy locations are on the priority list, subject to funding.

Protecting Habitat and Wetlands

Washington State has a wide diversity of habitats that support more than 650 native fish and wildlife species. As the population increases, and our human footprint expands, added pressure is placed on natural systems that are already heavily stressed in many cases. Habitat fragmentation, road kill, and wetlands loss are some of the impacts that transportation systems can cause.

Roads can fragment habitat for fish and wildlife, restrict the movement of wildlife across landscapes, and lead to vehicle collisions with wildlife (on average, 1,200 reported accidents,

134 injuries, and one fatality each year – in 2004, five people were killed in vehicle-wildlife collisions).

Nearly 900 WSDOT fish barriers have been identified for correction. The Washington Department of Fish and Wildlife has estimated there are another 33,000 non-WSDOT fish passage barriers located on city, county, federal, private, and tribal roads. So far, 140 WSDOT fish barriers have been fixed during the construction of a larger highway project, routine maintenance, or through the fish barrier retrofit program. Since 1991, 370 linear miles of stream habitat have been restored.

WSDOT adheres to wetlands protection requirements under Section 404 of the Clean Water Act and numerous state and local environmental provisions. At the same time, WSDOT is working with others to improve the effectiveness of wetlands protection and replacement requirements through opportunities for “watershed-based mitigation.”

This and many other important efforts, such as water conservation, herbicide use reduction, and native plantings along roadsides, can be found in the Gray Notebook.

Construction projects affecting wetlands can avoid or minimize impacts by selecting a different alignment, widening bridge structures, or adding retaining walls that limit the need for fill. To compensate for unavoidable wetland impacts, WSDOT has developed 116 mitigation sites, totaling 675 acres since 1987. Of the 53 sites (272 acres) that have completed monitoring since 1988, 49 (267 acres) have been judged successful.

Stormwater Runoff

When stormwater flows over roads and through roadway drainage systems, it carries pollutants originating from motor vehicles, the atmosphere, and other sources into surface water bodies. Sediments and pollutants (nutrients, oil, grease, and metals) are carried into rivers and streams in this way, affecting the quality and health of the water for people, animals, and plants.

Controlling the amount of flow is also important, as high flows can damage habitat, property, and transportation infrastructure. Managing stormwater flowing over transportation facilities is achieved through use of runoff treatment and flow control. Most of WSDOT’s stormwater outfalls were built prior to stormwater regulations and have no treatment facilities. To date, only 4,000 of WSDOT’s estimated 18,000 to 24,000 outfalls have been inventoried, so adequate data is lacking to prioritize outfalls for retrofit.