Planning For the Unplanned

March 1, 2024
How to improve transportation resiliency

By Rachel Blake, Jody Peace, and Matt Glasser, Contributing Authors

In June, a portion of the Interstate-95 overpass collapsed in Philadelphia after a tanker truck crash.

Though the city has opened a temporary six-lane roadway until the overpass is rebuilt, the collapse has affected commuters and commercial truck drivers who rely on I-95, one of the area’s primary transportation conduits.

An accident of this magnitude, coupled with the consequences on traffic and the supply chain, shines a light on the need for more resilient transportation infrastructure in the United States.

While major traffic incidents attract national media attention, incidents happen on a smaller scale nearly every day across the U.S. From car accidents to water main breaks, sporting events or construction, we experience traffic delays due to planned and unplanned disruptions all the time.

In many cases, the frequency of such events means that cities have become able to address and resolve such issues quickly, and motorists come to accept minor delays as business as usual. However, while cities are prepared to handle what we might consider typical disruptions, many are not prepared to apply these solutions to larger impacts.

Everyday impacts present opportunities to practice for large-scale events so that when major incidents occur, we can be better prepared for planned and unplanned events, making our transportation networks more resilient.

Unplanned Events

When Atlanta’s Interstate-85 bridge collapsed in 2017, the fire that caused it began during the middle of evening rush hour. The area was completely shut down, and traffic on the interstate and surface streets quickly formed a gridlock.

In minutes, engineers pushed down new traffic signal timing plans to major roadways to minimize the impact. Large-scale detour plans and restriping plans were developed overnight.

Within days, all traffic signals in a 2-mile radius of the collapse that had not yet been upgraded with new software or communication hardware were brought into the system and operated by a combination of consultant engineers.

Despite the potential for major traffic disruptions across the metropolitan area, delays were contained within a localized area.

The Georgia Department of Transportation (GDOT), along with many stakeholders, successfully managed this event thanks to the partnerships built that focused on surface street traffic operations.

The partnerships started with efforts to standardize traffic signal controllers and cabinets with the aim of easing maintenance, and it grew to standardization around remote communication methods, traffic signal software, and even naming conventions and detector configurations.

These wins built the backbone of the Regional Traffic Operations Program (RTOP), an active traffic management program with over 1,900 signals operated daily.

Since the I-85 bridge collapse, RTOP has evolved into a statewide program, encompassing over 9,000 traffic signals.

GDOT and many other stakeholders quickly and successfully activated the plan they had unknowingly been preparing for years.

They leveraged the technology they used daily to push the system harder, ramp up existing contracts with built-in flexibility, and organize over two dozen established partner agencies to deliver a single goal for the region.

Planned Events

Unplanned events, such as bridge failures or natural disasters, are often the primary focus of investment in network redundancy and discussions on network resiliency. However, the additional benefit of the investment in system redundancy and technology is to streamline the response to planned special events.

Planned special events are not ones that transportation professionals react to once they occur, but they have time to assess the impacts and prepare a response.

These can range from lane closures for a weekend 5K race to major sporting events attracting tens of thousands of fans. For smaller events, planners and engineers might have just a few weeks to develop mitigations while larger events may allow years. Irrespective of the magnitude however, these events are almost never planned far enough in advance to build new roadways.

In late 2013, the Atlanta Braves announced a plan to relocate the team to Cobb County, southeast of the city. The timeline allowed for over three years between the official announcement and the first event at the to-be-built stadium.

In the world of road construction, three years is barely enough time to build new turn lanes at an intersection, much less build new roadways. It was determined that beyond a few turn lane extensions, Cobb County engineers would be working with the existing transportation network. 

Fortunately, Cobb County had spent more than a decade investing in signal technology, including the installation of an adaptive signal system around the stadium.

This investment allowed Cobb County engineers, public safety officials, and Arcadis to spend the three years of planning focusing on how to optimize the existing system to provide a superior experience for fans. Ironically, opening day for the Braves would be during the I-85 bridge collapse response.

The biggest test came in fall 2021, when Cobb County hosted a parade to welcome the World Champion Atlanta Braves. Cobb County leaned heavily on its investment in technology to monitor and address vehicle and pedestrian traffic within the area before, during, and after the parade, including the closure of a six-lane roadway which carries nearly 34,000 vehicles per day.

Using a series of alternative routes and technology, Cobb County, GDOT, and Arcadis staff routed traffic around the area, responded to signal equipment needs, and coordinated lane closures.

After the parade, the team used cameras and remote signal timing capabilities to assist in clearing fans from the area and safely reopen the roadways. The use of this technology reduced delay, improved safety for attendees, and limited the need for field staff, which reduced resource needs and improved safety for staff.


As our transportation systems become more complex, so do the needs and expectations of the systems’ users. This makes use of technology even more essential.

Technology allows engineers and planners to be more efficient in their response to such events, increasing safety and reducing emissions. It is important that organizations are doing advanced planning for future events, investing in technology, and developing partnerships to help respond to these events. RB

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