A resilient transportation network can continue to provide seamless mobility even in the face of a changing climate. Inclement weather is currently estimated to cause 15 percent of congestion, increasing the number of crashes and delays and reducing road capacity. Approximately half of the days in a typical year have weather conditions that affect driving and contribute to road closures, traffic slowdowns, transit delays, crashes, and damage to electronic devices such as traffic lights, message signs, and cameras. These disruptions affect drivers, transit users, pedestrians, and cyclists, and the region’s most vulnerable residents are particularly affected by disruptions to the transit network. Climate change is already causing more frequent road flooding, snow storms, and heat- and cold-related pavement and communication failures. These capacity and performance issues are only expected to worsen.

As road and transit systems modernize, the same technologies that can improve system safety and reliability can make the system more responsive to weather events. The expansion of intelligent transportation system (ITS) devices and traffic management capabilities will support a variety of weather responsive traffic management strategies, such as instituting variable speed limit systems to reduce speeds during inclement weather, coordinating traffic signal timing that reflects the slower speed of travel in corridors during bad weather, employing alternative signal plans to support detours, and increasing coverage of emergency vehicle patrols to remove disabled vehicles more quickly. Existing regional strategies to mitigate impacts include traveler information and alerts, weather advisories, vehicle restrictions such as banning trucks during high winds, road closures for flooding or drifting snow, anti-icing/deicing road surface treatments, plowing, and pumping water from flooded locations.

The following describes strategies and associated actions to implement this recommendation.

Most of the region’s roads were designed using standards that pre-date the increased number of freeze-thaw cycles, heavy rain events, and hotter, wetter conditions posed by the region’s changing climate. Transportation modernization efforts should promote infrastructure that is built or retrofitted to revised design standards that take the anticipated climate of the region into account. Identifying locations at risk of flooding and then retrofitting these locations to handle current and future rain events can help maintain regional and local mobility, appropriately balance increased up-front costs with risk, and ensure that investments are built to last. The RTA, IDOT, and several county transportation agencies are already working to identify portions of the existing transportation system that are vulnerable to flooding and incorporating solutions into their long-range capital plans or operational response plans.

At the local level, municipalities must also address the vulnerability of their streets to flooding and other climate change impacts. Through the LTA program, CMAP could assist communities in vulnerability assessments to help inform capital improvement plans and corresponding design considerations. As new information on precipitation trends evolve and floodplain maps are updated, the local and regional vulnerability assessments should be updated periodically to reflect changing conditions. While the above assessments will help identify existing assets at risk of flooding, the region also should work to avoid expanding new streets and highways into flood prone areas. Avoiding road construction in floodplains may not always be possible; where necessary, such roads must be designed with future climate conditions in mind.

CMAP and transportation implementers should conduct studies to determine the vulnerability of transportation infrastructure to climate change impacts and design projects to accommodate the projected precipitation during its designed lifespan.

CMAP and partners should conduct a regional climate vulnerability assessment of the transportation system to inform long-range transportation planning and programming.

CMAP should develop a regional pavement flooding reporting system to help plan for flood events.

CMAP should incorporate climate resilience criteria into transportation programming processes.

State and local infrastructure agencies should review and update design manuals to ensure that the underlying climate data being used is up to date.

CMAP and partners should support continued efforts to integrate stormwater management into land use and transportation planning projects.

As the intensity and frequency of storm events increases with climate change, the region will need strategies to better integrate stormwater management into transportation planning and design. Best practices often include drainage improvements that increase detention capacity or promote infiltration, as well as a series of protective measures to reduce exposure to flood waters. Recently, the FAST Act expanded the scope of statewide and metropolitan transportation planning processes to reduce or mitigate stormwater impacts of surface transportation.^[1] This provision could enhance how stormwater management is addressed in overall planning efforts as well as individual surface transportation projects. Recent updates to the Surface Transportation Program (STP) program now incentivize the use of green infrastructure to manage stormwater.^[2]

Currently, highway and street design and reconstruction requirements do not reflect county-specific stormwater management goals or practices. Instead, they follow state design guidelines, which can limit the ability to implement green infrastructure and other innovative solutions or tailor design to local context and needs. Public rights of way often present good opportunities for green infrastructure. Many of our existing streets experience flooding due to development patterns in the surrounding area, particularly in communities developed prior to modern stormwater management standards. Street flooding could be addressed through infrastructure retrofits in surrounding neighborhoods instead of within constrained rights of way. Projects that comprehensively address stormwater management solutions can improve the performance of our transportation system while also reducing flooding damages in nearby neighborhoods. This strategy also appears in the Environment chapter under the recommendation Reduce flood risk to protect people and assets.

Local governments should support continued efforts to better integrate stormwater management into land use and transportation planning projects.

IDOT should update statewide design standards to reflect green infrastructure techniques and precipitation trends, designing transportation infrastructure for the climate of its designed lifespan.

Transporation agencies should construct and maintain projects that can sufficiently manage current and future storm events.

IDOT should support CMAP’s stormwater management planning efforts to reduce flooding vulnerability of the transportation system.

Counties and municipalities should update development ordinances and reconstruction practices to improve stormwater management and promote green infrastructure techniques in new and reconstructed streets.

Climate change is already causing more frequent road flooding, snow storms, and heat- and cold-related pavement and communication failures. Inclement weather is currently estimated to cause 15 percent of congestion, increasing the number of crashes and delays and reducing road capacity. Approximately half of the days in a typical year have weather conditions that affect driving.^[1]  Pedestrians and transit users are also affected by inclement weather, and pedestrian infrastructure is often overlooked in weather response activities.

Existing regional strategies to mitigate impacts include traveler information, alerts and advisories, vehicle restrictions such as banning trucks during high winds, road closures, snow and ice control, plowing, and pumping water from flooded locations. IDOT, the Tollway, and Lake County report real-time “road weather” (pavement) information to TravelMidwest, but other counties currently do not. Weather responsive traffic management is also not widely used today, except for closing roads to traffic under severe conditions. As road and transit systems modernize, the same technologies that can improve system safety and reliability can make the system more responsive to weather events. The expansion of intelligent transportation system (ITS) devices and traffic management capabilities will support a variety of weather responsive traffic management strategies, such as variable speed limits to reduce speeds, updating traffic signal timing and plans to support detours and slower speeds, and increasing coverage of emergency vehicle patrols to remove disabled vehicles more quickly. In addition, as the region’s maintenance fleets become equipped with fleet management technology, opportunities for better coordination of snow and ice removal between different jurisdictions will emerge. This will reduce costs and improve the efficiency of these activities.

It will be important to collect and analyze information about how facilities perform under various severe weather scenarios so agencies can develop planned responses and better serve all users of the transportation system. For example, focusing incident management resources on locations that are known to be affected by rain or snow can reduce congestion and secondary incidents. Pavement flooding information has not been collected on a regional basis, and there is no standard pavement flooding reporting system. The impact of flooding on our roadway operations as of today is not known. This strategy also appears in the Environment chapter under the recommendation Plan for climate resilience.

CMAP, and IDOT and the Tollway should work toward implementing a regional, multijurisdictional traffic management center, either virtual or traditional.

Transportation agencies should ensure redundant and reliable electricity and communications infrastructure, and build redundancy and flexibility into planning for major transportation corridors.

Transportation implementers should expand ITS devices and traffic management capabilities to support weather responsive traffic management strategies.

Transportation implementers should coordinate snow and ice removal across jurisdictions, when possible.

Transportation operators should conduct an analysis of road performance under severe weather conditions to develop planned responses.

CMAP should develop a regional pavement flooding reporting system to help plan for flood events.