I-59/20 Central Business District Bridge Replacement

What the locals refer to as Malfunction Junction is the area in Birmingham, Alabama at the I-59/20 interchange between I-65 and the Red Mountain Expressway. True to its nickname, Malfunction Junction has become a monster of a problem not just because of its bumpy roads, wrecks, and traffic jams but also because of its aging bridges. These bridges carry over 160,000 vehicles per day – twice the amount of daily traffic for which they were designed. Ready to say goodbye to the malfunction, Alabama Department of Transportation (ALDOT) began several years ago a plan to revitalize this infrastructure by removing and replacing the elevated bridge sections of I-59/20 between I-65 and US-280/Red Mountain Expressway. The project’s main purpose was to replace the old bridges that had exceeded their service life as well as to consolidate and reconfigure the ramps, reducing traffic congestion and improving safety in the area.

In 2012 ALDOT tasked Sain Associates with re-designing the Intelligent Transportation Systems (ITS) devices that provide vital communication and traveler information. Prior to the I-59/20 bridge replacement construction work, we designed and ALDOT installed cameras, traffic data collectors, and message boards several miles outside of the Central Business District (CBD) area to communicate messages to drivers in time for them to have an opportunity to adjust their routes accordingly. ALDOT also used the data collected to measure the traffic patterns and congestion in these same areas. Cameras and traffic data within the project work zone allowed ALDOT to monitor construction and detour routes.

Before construction could begin, ALDOT had to remove a key fiber optic backbone cable that was attached to the I-59/20 bridges. To maintain critical communication between ALDOT and its traffic monitoring devices, a new fiber optic backbone was installed to take over the communication prior to the bridge and attached fiber optic cable being removed.

In addition to the ITS, Sain Associates evaluated projected traffic conditions associated with the 12 to 14 month period when I-59/20 would be closed between I-65 and US-280. By using traffic modeling software, we located potential deficiencies and recommended improvements.  Our findings showed that several detour routes needed improvements to accommodate the projected traffic increases during construction. We also used travel demand modeling to forecast traffic volumes for the key detour routes and the north grid of downtown Birmingham. This area included over 150 traffic signals, and we created temporary signal timing plans for this entire system to keep traffic moving efficiently across downtown. The recommended improvements and temporary signal timing plans were all successfully developed and implemented prior to the closure date.

After seven years of planning, I-59/20 CBD bridge closure started on the evening of Monday, January 21, 2019. During the first week of the closure, Sain Associates’ traffic engineers assisted with 24/7 staffing of the ALDOT Region Traffic Management Center (RTMC) along with other members of ALDOT’s project design, maintenance, operations, and construction teams. We assisted in monitoring traffic using a combination of camera feeds, the AlgoTraffic app/website, and frequent driving of the detour routes during peak periods of traffic congestion. We also adjusted the signal timing as the detour traffic patterns began to settle.

A project of this magnitude is naturally going to have some challenges, one being the effects of GPS-based navigation systems. A driver’s GPS often suggested routes that were different from the marked detour routes, which created traffic congestion in unanticipated areas. To combat this issue, we had to adjust signal timing after closures began, fixing traffic congestion in real-time. 

Another challenge was the age of the traffic signal and communications equipment along the marked detour routes. This led to some difficulty in programming and adjusting signal timings before and during the detour period. Upgrading the old signal and communications equipment along the marked detour routes would have been a good addition to the overall project.

The reconstruction of I-59/20 is almost complete, and the bridges were re-opened to traffic in mid-January 2020. Traffic planning and engineering continues as we are developing and implementing permanent signal timing plans for the reconfigured system. We are excited to see the end result of this expansive project and how it will improve the daily commute of our community.

Being given the opportunity to collaborate with professionals on this project in our hometown has been a privilege. We hope the next time you drive through Birmingham you will be able to appreciate the thought and collaboration that went into this improvement.