Increased temperatures, extreme precipitation events, and rising sea levels represent threats to many elements of the United States' land-based transportation system. Extreme weather and climate-related events can damage infrastructure, increase maintenance needs, and interrupt normal operations of roads, bridges, railways, and vehicles. In our fast-paced economy, any disruption of the transportation network can delay the delivery of materials, goods, and people, triggering a cascade of delays and economic impacts across multiple systems.
While a range of potential climate impacts threaten transportation systems, generally the most significant and long-lasting impacts are likely to involve damage to infrastructure from flooding associated with extreme precipitation or sea level rise. The most serious damage to this infrastructure is often associated with scour, erosion, or wave action rather than inundation.
As climate conditions change, events such as flooding of the Mississippi River in 1993—an event that halted east-west truck and rail traffic for six weeks—may occur more frequently. In addition to reducing economic activity across the nation, these events can cause physical damage to transportation infrastructure, incurring costs for repair and replacement. Increased exposure to moisture associated with more frequent storms can impact the structural integrity of roads, bridges, and tunnels. For instance, in Louisiana, long-term submersion of approximately 200 miles of roadway caused nearly $50 million in damages. Additionally, increases in the heaviest precipitation events may increase washouts of roads and scouring of bridge supports. As more precipitation falls as rain rather than snow, erosion can become a larger factor in damaging roads, bridges, and railways.
In coastal areas, increases in strong hurricanes and sea level have the potential to damage land-based transportation. In the Gulf of Mexico, for instance, a storm surge of 18 feet could inundate one-third of railways in the region. Sea level rise expected by 2100 will make an additional 2,400 miles of major highways in the Gulf Coast subject to permanent flooding. Land-based transportation infrastructure in the Gulf Coast supports economic activity worth hundreds of billion dollars each year, and these assets are increasingly at risk from climate-related impacts.
Increased temperatures may affect land-based transportation through asphalt road degradation, rail buckling, thermal expansion of bridges, and changes in maintenance schedules. Road and rail systems are typically engineered to withstand particular temperature ranges, based on anticipated future weather. When temperatures exceed the range for which they were designed, pavement can soften, rails can kink, and steel structures can expand, leading to pavement failure, derailments, and accelerated deterioration. Increased temperatures may also impact maintenance schedules of roads and railways due to concerns over the health and safety of outdoor workers, who could face heat exhaustion if required to work in high temperatures.
Higher temperatures can cause additional issues for land-based transportation systems in various regions. For instance, much of the transportation infrastructure in Alaska is built on permafrost, which provides a stable building foundation so long as it remains frozen. When permafrost thaws, however, roads and runways it has supported may slump. Also, in regions where drought conditions are present, increased temperatures increase the risk of wildfire. Increasing frequency, magnitude, and duration of wildfires pose risks to roads, bridges, and railroads. Increased temperatures may also benefit the transportation system in some regions by reducing maintenance costs related to de-icing and enabling construction and repair crews to work over a longer season.
This section is excerpted and abridged from the report Climate Change Impacts in the United States: The Third National Climate Assessment (Chapter 5: Transportation).