One particularly large issue facing today’s cities is all about cohabitation.
How do we fit modern transit and infrastructure, crucial to growing populations, into cities with aging historic architecture?
Dallas, Texas encountered this issue with its plan to build a streetcar line between Dallas’ central business district and its Oak Cliff neighborhood. Although relatively short (1.6 miles of track), the line was more than a century in the making.
Building on the Houston Street Viaduct
The Houston Street Viaduct in Dallas, Texas is now home to a new streetcar system.
The Houston Street Viaduct is a historic bridge in Dallas spanning the Trinity River. When construction ended in 1910, the bridge was the first permanent crossing of the flood-prone river. Electric streetcars were prevalent in Dallas at the time of the bridge’s construction and 1912 plans included accommodation for streetcar rail lines that in the end were never built.
While the viaduct was designed with a streetcar system in mind, it wasn’t until December of 2010 that DART (Dallas Area Rapid Transit), the city’s transit agency, received a Transportation Investment Generating Economic Recovery (TIGER) grant—the U.S. Department of Transportation’s attempt to match NASA’s acronym-related wit—to start the project in conjunction with the city and the North Central Texas Council of Governments (NCTCOG).
The plans for the section of the streetcar line over the bridge were complicated at best, being a retrofit to a structure that has been standing for 100 years. It would require a single track that would serve as a bi-directional passage for the cars and would also feature approximately one mile of the line running without overhead wires—a first in the United States.
International Collaboration Using BIM
The streetcar was a large-scale project, involving 70 team members in 18 offices across the globe. In order to save time and overcome time zones, engineering firm HDR incorporated building information modeling (BIM).
A rendering shows the streetcar running without wires across the bi-directional track. (Image courtesy of Bentley Systems.)
The company used Bentley’s ProjectWise platform to organize international offices. This strategy let the team work on the project’s 17,000 files collaboratively and work between various BIM software suites, including InRoads, GEOPAK, Descartes as well as other external applications.
Construction on the project began in March 2013 and the line opened to the public in April 2015.
The integration success of the project landed it a seat at the Bentley Be Inspired Awards in November 2015, where it took home special recognition for Advancing Integrated Projects.
A Combination of Modern and Historic
Retrofitting historic infrastructure to suit new systems is a tricky task. There’s a delicate balance between modernizing a structure just enough and too much—and the difference can cause a social uproar if the historic character is adversely affected.
The Dallas Streetcar is an example of a modern transit system coexisting with historic architecture without disturbing the waters. Although the bridge is over a century old, it was originally designed to accommodate a streetcar system and the lack of overhead wires keeps the streetcar unobtrusive.
For more information about the project, check out the HDR website.