How a rising tactic in bridge design and construction is bringing welcome relief to drivers and communities alike
There’s a necessary evil in our work upgrading bridge infrastructure—managing traffic and vehicle congestion. Bridge construction can force commuters into frustratingly long detours, block homeowners from convenient access to their homes, and, at worst, even impact emergency services.
This congestion can be especially maddening for drivers who are regularly navigating through a job site that has encroached upon the road or highway by restricting lanes for what seems to be a slow-moving construction project, oftentimes for highly complex and necessary infrastructure upgrades like bridge replacements. In my years overseeing the design and construction of bridges and roadways throughout New England, particularly along the bustling expressways in Greater Boston, balancing a project timeline while minimizing impact on local traffic patterns has always been a highly complicated endeavor.
Luckily, in recent years there’s been some relief with new methods and tactics designed to help mitigate the downtime of roadways and highways during construction.
The River Street Bridge project in Boston involved the replacement of a busy multi-modal crossing for pedestrians, daily vehicle traffic, and a bus route, which was also located above a railroad.
The ABCs of accelerated bridge construction
Like many states across the US, Massachusetts state officials have embraced a new approach. In 2008, the Massachusetts Legislature established Accelerated Bridge Program legislation to launch this concept with the goal of reducing the number of structurally deficient bridges in the state system and (arguably most importantly) doing this work in a way that causes the least amount of disruption to the traveling public.
By using prefabricated/precast bridge elements or constructing as much of the new bridge as possible off-site and then installing the new bridge in place of the old, accelerated bridge construction (ABC) can speed replacement or rehabilitation of workhorse bridges to reduce mobility impacts and user costs. Benefits of this practice include faster delivery time, improved work-zone safety for the traveling public and project crews, minimized traffic impacts, and a shortened window of disruption to the local community in terms of noise, detours, and traffic. With about one-quarter of the nation's 600,000 bridges needing rehabilitation, repair, or replacement, ABC can serve as a valuable tool.
ABC can come with its own unique challenges—namely the need for ample space for project staging and laydown. However, I’ve found that these techniques can be especially valuable in densely populated, congested areas where minimal disruptions to traffic and transit are vital, including bicyclist and pedestrian traffic.
_q_tweetable:With about one-quarter of the nation's 600,000 bridges needing rehabilitation, repair, or replacement, accelerated bridge construction can serve as a valuable tool._q_
Managing multi-modal needs
Our team at Stantec has been at the forefront of utilizing ABC in New England, and we’ve had great success employing ABC in areas like Boston, where the needs of local drivers, pedestrians, and public transit must be considered. Most recently, we designed two bridge replacements in Boston’s thriving Dorchester neighborhood that both illustrate how effective collaboration and planning can help minimize disruptions to the local community.
The River Street Bridge and Morton Street Bridge replacements posed a unique challenge, with both projects occurring on a bus route, as well as over a railroad used by the Massachusetts Bay Transportation Authority (MBTA) and CSX freight railroad. As a result, construction phasing required close coordination with MBTA’s commuter rail operators, CSX freight operators, and bus route operators to detour traffic while also maintaining vehicular and pedestrian access to all local streets and businesses.
Through proactive collaboration and construction planning, each bridge was replaced in a 55-hour window, only impacting vehicular and rail traffic for two separate weekends.
Preserving accessibility in a city’s center
Our team also developed plans for the rehabilitation of Massachusetts Avenue bridge over Commonwealth Avenue in the heart of Boston’s bustling Back Bay neighborhood. This work was essential to improving the condition of the bridge—originally built in 1937—and enhancing safety conditions. In this case, a conventional replacement would require up to three years for construction, resulting in ongoing disruptions to Massachusetts Avenue as well as Commonwealth Avenue crossing underneath.
Accelerated bridge construction helped ensure limited disruption during the rehabilitation of Boston’s Massachusetts Avenue over Commonwealth Avenue, which sees an average of 22,000 daily drivers.
As a key artery in Boston with a 22,000 average daily traffic estimate, the team was challenged with maintaining traffic (for vehicles, buses, bicyclists, and pedestrians) and utilities during construction. As a result, we utilized ABC to ensure accessible traffic lanes on Massachusetts Avenue and limited public disruption. A unique aspect to this project involved the relocation of all utilities away from the bridge before demolition and replacement could occur. Once complete, work was accomplished over Mother’s Day weekend, with the contractor ultimately being able to open Massachusetts Avenue to traffic one day ahead of schedule.
While the concept of ABC is easy—build a bridge off-site in the biggest pieces possible to allow you to assemble it on-site in the shortest amount of time—the condensed timeframe requires a very experienced engineered approach to coordinating all pieces in a temporary bridge closure. Done well, this results in satisfied drivers, rail commuters, bicyclists, and walkers, who experience minimal disruptions to their daily lives.
About the AuthorMore Content by Walter Heller