If one word had to describe the condition of infrastructure across modes this summer, a top contender is “hot.” Increased temperatures and periods of extreme heat this summer highlighted vulnerabilities across global transportation systems. In the continental U.S., July 2026 was the hottest month on record.

The impacts of extreme heat have been felt on U.S. roadways, bridges, runways, rail tracks, on riders, and by both travelers and transportation workers. Impacts this summer have included blowups on Interstate 49 in Louisiana, a movable bridge in New Jersey closed on various occasions from June to August, and U.S. Highway 69 exploding at a pavement joint in Greenville, Texas.

Across modes and usages, a common theme emerges: contemporary transportation infrastructure is not designed for the extreme levels of heat being experienced as the frequency and severity of high temperatures increases. Those in charge of affected transportation systems must respond to heat-induced increased stress on infrastructure systems, with mitigation techniques including but not limited to: flight cancelations and limitations on the number of people on flights, painting pavement white to reduce heat, and slowing train speeds. At the same time, transportation agencies, airport operators, and rail operators must be planning for a present and future with higher average temperatures.

Multimodal Infrastructure Impacts

Heat related infrastructure disruptions do not discriminate by mode and can be multimodal in their impact. Movable bridges are at particular risk of operational delays due to heat because heat can disrupt the mechanical mechanisms that open and close bridges. In 2024, New York’s Third Avenue Bridge could not close for roadway traffic because metal in the bridge expanded while it was open for maritime traffic. Extreme temperature fluctuations can also cause accelerated deterioration of the concrete and steel within a bridge.

Roadways are designed with space for the concrete to expand and contract as temperatures change within a certain range. However, extreme and frequent temperature increases have resulted in expanding concrete to the point of roadway buckling. Many roads are currently built with asphalt grades that are not appropriate for the levels of heat that are becoming increasingly more common. Asphalt softens in heat and can then be reshaped as vehicles travel, creating bumps and ruts.

Heat also endangers rail-based transportation. During heat waves Amtrak has had to cancel or delay trips. Heat results in the expanding of rail which can result in the buckling of tracks due to pressure, also described as a “sun kink.” Washington Metro triggers inspections when rails reach 135 degrees.

Heat is also problematic for electrified transportation as heat negativity impacts electricity transmission (such as causing line sagging) and can generate demand overruns as people and systems seek to cool off. The Los Angeles County Metropolitan Transportation Authority has implemented spring-loaded tensioners to support catenary lines in a hotter

Cancellations also occur at airports as higher temperatures reduce air density. Reduced air density makes takeoffs more difficult, particularly for airports with shorter runways. To combat this, airlines have reduced the number of passengers to make takeoff easier or have had to completely cancel flights when take-off is not viable. The high amount of concrete infrastructure at airports and lack of shade and green space can make them concentrated areas of heat. (Ed. Note: Ironically, 20-30 years ago, the fact that airports are heat islands was used by doubters to deny the pervasiveness of global warming because most U.S. heat records are kept by weather stations at airports.)  Southwest Airlines has flagged heat waves as a significant physical threat to their future operations.

Human Impacts

Heat is not only a threat to infrastructure itself but also to those moving through and working on transportation infrastructure systems. Heat is the most fatal form of extreme weather in the United States.

Construction season in the United States peaks in the summertime, increasing the likelihood that construction workers will encounter high temperatures. From 1992 to 2016, there were approximately 285 construction deaths tied to heat exposure. As temperatures rise, productivity and safety decline, with productivity decreasing by 25% when temperatures are at or above 90 °F and by 70% when temperatures are at or above 100 °F. In hotter worker conditions, transportation workers must be encouraged to take breaks and have access to water and other cooling mechanisms. The impacts on the transportation workforce from heat also include impacts on bus and transit operators.

Passengers may be disincentivized from utilizing public transportation as heat makes public transit travel less comfortable and potentially unsafe. Bus and transit services should have adequate cooling systems to ensure both transit operators and riders can remain cool. Changes to the built environment surrounding transit, such as canopy cover and bus shelters with shade can help to create a cooler experience for riders. Additionally, increased tree cover helps to combat the urban heat island effects.

The Inflation Reduction Act included significant investment in the Forest Service’s Urban and Community Forestry Program to help states and local governments expand community forests. Additional federal programs that have in the past supported enhanced extreme heat resilience under the Infrastructure Investment Jobs Act include the Heathy Streets Program; Neighborhood Access and Equity programs; and the PROTECT Program (Promoting Resilient Operations for Transformative, Efficient, and Cost-Saving Transportation). New York City recently launched its Urban Forest Plan with the goal of increasing tree canopy cover to 30 percent by 2040. NYC Parks Commissioner Tricia Shimamura described tree cover as a “living infrastructure to keep our city cool.”

Financial Impacts and Mitigation

Not only do these infrastructure problems create service and travel delays but they also come at a financial cost for transportation agencies and operators. According to one estimate, the financial impact of heatwaves on infrastructure could reach $19-26.3 billion by 2040 due to new maintenance and replacement costs. In 2020, it was estimated that heat exposure loss of productivity resulted in a loss of $100 billion, with this loss expected to increase to $500 billion by 2050. In the transportation sector, the cost of extreme heat includes but is not limited to faster denegation of infrastructure, the need for enhanced maintenance, the economic costs of delays, and the impact on labor productivity.

Heat resilience can be built into design and planning standards by transportation agencies. In doing so, transportation agencies must consider long-term projections for heat increases and the level of risk they are willing to take on. In 2023, the Federal Highway Administration emphasized the importance of utilizing predicative models rather than historic climate records in designing new infrastructure projects. While hardening measures may bring additional cost to projects in the near term, not preparing infrastructure for a hotter future will likely be more costly in the long term if infrastructure is not built to withstand more extreme temperatures.

Areas in the United States, such as the Southwest, that more regularly experience higher temperatures can provide important lessons as extreme heat becomes more universal. Phoenix has a specific Office of Heat Response and Mitigation which has implemented a Cool Pavement Program and a Cool Corridor Program. The Cool Pavement Program paints roadways with solar-reflective coating to decrease surface temperature. The Cool Corridor Programs aims to increase shaded coverage of roadways.

Measures to build resilience into rail infrastructure include (but are not limited to) the use of heat-resistant steel and updates to track design. In roadways, engineers can utilize sawed joints filled with sealant or stronger concrete. For movable bridges, cooling systems may be required in the future. Resilience measures can also be lower cost, such as white paint and increase tree cover.

Just as the impacts of extreme heat on transportation are multifaceted, resilience does not exist through a single solution. Multifaceted resilience can look like changes to physical infrastructure such as infrastructure materials, increased flexibility for expansion, cooling systems, and longer runways. Resilience must also include changes to the surrounding built environment such as canopy cover and cooling locations for transportation users and workers. Resilience additionally must be a part of operational design and decisions, such as the intensity of flight and rail travel that can occur during heat waves. U.S. agencies can also learn from strategies from other countries experiencing extreme heat. During a heat wave in June in France, workers who had the ability to were encouraged to work remotely, and in London rail frequency was reduced this summer during extreme periods of heat.

As it gets hotter, flexibility in infrastructure design and operations will become key. Transportation agencies with a core mission of safety must take into account the risks that extreme heat presents to transportation infrastructure and users. The additional costs of mitigation and resilience measures must be placed in context of the current and projected impacts of heat on contemporary infrastructure systems.