First Streetcar in U.S. to Incorporate Off-Wire Technology

• Spurred community revitalization and improved mobility and connectivity
• Eliminated 2.7 tons per day of CO2 emissions
• First streetcar in the United States to use flash butt welding
• First modern streetcar in Texas
• Second streetcar in the U.S. to use block rail
• Repurposed an historic ASCE civil engineering landmark while maintaining its aesthetic character

The Union Station to Oak Cliff Dallas Streetcar Project (Dallas Streetcar) started as a guided-rail transit system that would link residents of the Oak Cliff borough with downtown Dallas. Winning multiple awards, spurring extensions and driving development in the economically distressed community of Oak Cliff, this roughly $28.7 million, 1.6-mile starter streetcar has turned into much more than a simple means of transportation. To make Dallas Streetcar possible, HDR partnered with the city of Dallas and Dallas Area Rapid Transit (DART). We led final design services for the Stacy and Witbeck/Carcon Industries design-build team.

History Becomes the Future

The community of Oak Cliff is separated from the heart of Dallas by the Trinity River and its sprawling floodplain, a geographic feature that inspired many design innovations in Dallas Streetcar and the shared-use pathway that accompanied its construction. The streetcar and pathway traverse the river and floodplain across Houston Street Viaduct, which was constructed in 1911 and is on the National Register of Historic Places.

Ironically, the viaduct's 44-foot-wide deck was originally conceived to support two trolley lines for a future streetcar system but the rails conceived were never laid. And by the time design commenced for Dallas Streetcar, the viaduct’s historical status precluded installing overhead catenary towers and cables such as are used on modern streetcars.

Dallas needed an innovative approach and our team helped create one.

Our design team devised a streetcar that operates exclusively off stored energy for two thirds of its total route and is re-charged during the other third. And when Dallas Streetcar opened in April 2015, the century-old promise of a streetcar system across Houston Street Viaduct was finally fulfilled — in a way not possible back then yet consistent with the viaduct’s historic character.

Supported by 51 concrete arches, the picturesque viaduct’s preservation was paramount, and was a prime consideration for the streetcar alignment. It ultimately led to another innovation: the use of relatively exotic block rail.

Choosing block rail reduced the dead load placed upon the mile-long, 104-year-old structure. A single-track, bi-directional alignment constructed with block rail inherently weighs less because of block rail’s smaller profile. At the same time, block rail requires a shallower track slab, which means less concrete and less weight. There was only one problem: block rail was not being manufactured in the United States.

Importing might have been an option except that $23 million of the funding for Dallas Streetcar came from a Transportation Investment Generating Economic Recovery (TIGER) grant. That grant stipulates American-made materials. So we went to Poland and came back with specifications to manufacture 112Tram block rail. This rail is now manufactured in the U.S. and has become the standard for all streetcar extensions in Dallas.

A side benefit to block rail’s shallow profile is its flush installation since bicycles cross the Dallas Streetcar alignment at grade, and cars drive over it to change lanes.

The block rail was then welded together using flash butt welds rather than more traditional thermite welds, becoming the first streetcar in the U.S. to do so and shaving about 45 days off construction time.

“Regional Connections — Linking Livability”

This was the theme of Oak Cliff Transit Authority’s 2010 application for a TIGER grant.

It combined ideas for integrating housing and employment with rail transit: walkable, mixed-use neighborhoods on the Oak Cliff side of the viaduct; and downtown Dallas’s robust commerce and medical services at the other end.

After a year and a half in service, the arrival of the Dallas Streetcar has driven up demand for property along its alignment. By September 2016, brownfields were still transitioning to mixed-use developments. Neither bus lines nor major roads built in the preceding 30 years had triggered as much walkable development as Dallas Streetcar triggered in Oak Cliff. Bicycle and foot traffic, outdoor seating and a visible sense of community continue to flourish on either side of Dallas Streetcar.

Not Without Challenges

When we started the final design, we uncovered design changes needed to the preliminary engineering plans that would require a revision to the Environmental Assessment (EA), a process that had the potential to put the project behind schedule.

We helped prevent that by dividing our design into four design packages that allowed construction to continue during the extended EA approval. Early adoption of Building Information Modeling (BIM) enhanced our ability to do this, and it was a recipe for success. Dallas Streetcar opened April 13, 2015, and since the starter line opened, a .7-mile extension has been added to the Bishop Arts District.