The U.S. economy depends on the personal and freight mobility provided by the country’s transportation system. Essential products and services like energy, food, manufacturing, and trade all depend in interrelated ways on the reliable functioning of these transportation components. Disruptions to transportation systems, therefore, can cause large economic and personal losses.72 The national transportation system is composed of four main components that are increasingly vulnerable to climate change impacts:
- fixed node infrastructure, such as ports, airports, and rail terminals;
- fixed route infrastructure, such as roads, bridges, pedestrian/bicycle trails and lanes, locks, canals/channels, light rail, subways, freight and commuter railways, and pipelines, with mixed public and private ownership and management;
- vehicles, such as cars, transit buses, and trucks; transit and railcars and locomotives; ships and barges; and aircraft – many privately owned; and
- the people, institutions, laws, policies, and information systems that convert infrastructure and vehicles into working transportation networks.
Besides being affected by climate changes, transportation systems also contribute to changes in the climate through emissions. In 2010, the U.S. transportation sector accounted for 27% of total U.S. greenhouse gas emissions, with cars and trucks accounting for 65% of that total.73 Petroleum accounts for 93% of the nation’s transportation energy use.73 This means that policies and behavioral changes aimed at reducing greenhouse gas emissions will have significant implications for the various components of the transportation sector.
Weather events influence the daily and seasonal operation of transport systems.56,55,54 Transportation systems are already experiencing costly climate change related impacts. Many inland states – for example, Vermont, Tennessee, Iowa, and Missouri – have experienced severe precipitation events, hail, and flooding during the past three years, damaging roads, bridges, and rail systems and the vehicles that use them. Over the coming decades, all regions and modes of transportation will be affected by increasing temperatures, more extreme weather events, and changes in precipitation. Concentrated transportation impacts are likely in Alaska and along seacoasts.
Climate trends affect the design of transport infrastructure, which is expensive and designed for long life (typically 50 to 100 years). The estimated value of U.S. transportation facilities in 2010 was $4.1 trillion.74 As climatic conditions shift, portions of this infrastructure will increasingly be subject to climatic stresses that will reduce the reliability and capacity of transportation systems.1 Transportation systems are also vulnerable to interruptions in fuel and electricity supply, as well as communications disruptions – which are also subject to climatic stresses.1,75 For example, power outages resulting from Hurricane Katrina shut down three major petroleum pipelines for two days, and the systems operated at reduced capacities for two weeks.76
Climate change will affect transportation systems directly, through infrastructure damage, and indirectly, through changes in trade flows, agriculture, energy use, and settlement patterns. If, for instance, corn cultivation shifts northward in response to rising temperatures, U.S. agricultural products may flow to markets from different origins by different routes.77 If policy measures and technological changes reduce greenhouse gas emissions by affecting fuel types, there will likely be significant impacts on the transportation of energy supplies (such as pipelines and coal trains) and on the cost of transportation to freight and passenger users.5
Shifts in demographic trends, land-use patterns, and advances in transportation technology over the next few decades will have profound impacts on how the nation’s transportation system functions, its design, and its spatial extent. As transportation officials shape the future transportation system to address new demands, future climate conditions should be considered as part of the planning and decision-making process.
Disruptions to transportation system capacity and reliability can be partially offset by adaptations. Transportation systems as networks may use alternative routes around damaged elements or shift traffic to undamaged modes. Other adaptation actions include new infrastructure designs for future climate conditions, asset management programs, at-risk asset protection, operational changes, and abandoning/relocating infrastructure assets that would be too expensive to protect.2 As new and rehabilitated transportation systems are developed, climate change impacts should be routinely incorporated into the planning for these systems.
There will be challenges in adapting transportation systems to climate related changes, particularly when factoring in projected growth in the transportation sector. A National Surface Transportation Policy and Revenue Commission in 2007 forecast the following annual average growth rates: average annual tonnage growth rates of 2.1% for trucks, 1.9% for rail, and 1.2% for waterborne transportation, and an average annual passenger vehicle miles traveled growth rate of 1.82% through 2035 and 1.72% through 2055.78