RESILIENCE METRICS FOR TRANSPORTATION
A safe, efficient, and accessible transportation system is critical to a thriving community. When climate hazards affect our transportation infrastructure, there can be cascading impacts to many other sectors and services. Climate hazards affecting transportation infrastructure can include both long-term stressors (such as increased extreme heat) that accelerate degradation of the infrastructure over time, and short-term shocks (such as more frequent severe storms) that have immediate impacts. By assessing the vulnerabilities of our transportation infrastructure to changing climatic conditions, we can make ourselves more resilient to these impacts.
The table below provides an overview of the total climate vulnerability scores for Fairfax County’s roadways, public transit systems, and bicycle and pedestrian networks. These vulnerability scores were based on a combination of exposure (how exposed is the infrastructure to the hazard, and is that hazard increasing or decreasing?), sensitivity (when the infrastructure is exposed, does something bad happen?), and adaptive capacity (can the infrastructure adapt to changing conditions?). For a detailed description of vulnerabilities, please see the Climate Vulnerability and Risk Assessment. An interactive map of these natural resources and certain climate hazards can be found in the Resilient Fairfax Interactive Map Viewer.
Roadways, Bridges, and Electric Vehicle Infrastructure Vulnerabilities
The roadway system in Fairfax County is largely owned and maintained by the Virginia Department of Transportation (VDOT). Very few public roads are owned by the Fairfax County Department of Transportation (FCDOT). The Dulles Toll Road is under the authority of the Metropolitan Washington Airports Authority. The George Washington Memorial Parkway is under the authority of the National Park Service. In addition to public roads, there are privately-owned and maintained roads throughout the county, as visualized in this map. Roadways, bridges, and EV charging stations have a moderately high vulnerability to extreme heat, and a high vulnerability to inland flooding and severe storms.
Roadways are highly vulnerable to flooding, which is one of the top hazards in Fairfax County. Roadway flooding, closures, and swift water rescues are reported in different ways. Data from 911 calls are one source of this information. In Fairfax County, between June 2013 and October 2023, (3,710 days), there were 576 days with 911 records of roadway flooding, including roadway closures, water-related hazards, and swift water rescues. This means that on average, 16% of days in Fairfax County have 911 calls related to roadway flooding.
Certain roadways flood much more often than others. The graph here shows the top 20 roadways that appeared in 911 reports for flooding. (911 data courtesy of Fairfax County Departments of Emergency Management, Fire and Rescue, Police, and Public Safety Communications).
Flood-compromised roadways are a serious safety concern, increasing the risk of road accidents, drownings, and reduced ability for emergency personnel to deliver aid. In addition to the vulnerabilities of the people using the transportation infrastructure, (which is the top priority), transportation infrastructure itself is sensitive to flooding. Flooding of roadways and bridges can cause erosion, structural failure, deterioration, debris, and overflowing of drainage systems, inflicting damage on surrounding environments and compromising road safety.
Fairfax County prioritizes flood-prone areas for flood risk reduction and transportation improvement projects. For example, Old Courthouse Road is one of the top flooding locations, and it is currently being upgraded to reduce flood risk and other issues. (See the Old Courthouse Road Realignment Project here). For an interactive map of several flooding types, please see the Resilient Fairfax Interactive Map Viewer.
Transportation Infrastructure and Extreme Heat
Extreme heat is another top vulnerability for roadways, bridges, and electric vehicle infrastructure. 73% of roadway miles, 61% of bridges, and 98% of electric vehicle charging stations are in Urban Heat Islands, where land surface temperatures are significantly hotter. This is partially because transportation infrastructure itself (such as asphalt) can increase the Urban Heat Island effect by staying much hotter than green space. However, these heat islands also create vulnerabilities for the infrastructure itself.
Exposure to higher temperatures can damage and degrade transportation infrastructure more quickly, causing pavement to crack and EV chargers to malfunction. Most electric vehicle chargers operate optimally between -13F and 104F and can become dangerous in higher temperatures and humidity that is conducive to electrical arcs.
The map here shows an urban heat island with transportation infrastructure from the Resilient Fairfax Interactive Map Viewer. For additional roadway vulnerabilities, including those related to severe storms, please see the Vulnerability and Risk Assessment. For information on what the county is doing to boost resilience, please see the Resilient Fairfax plan.