With a deep desire to provide a safer, more reliable travel experience through Travis County, TxDOT initiated the I-35 Future Transportation Corridor (FTC) Planning and Environmental Linkages study. Its purpose was to determine the ideal lane type and mode choice for the FTC, and results pointed to the integration of a managed lane system (one lane in each direction).
TxDOT hired our team to create schematics for this proposed solution, which consisted of ingress and egress points for the managed lane as well as intersection and rail line reconfigurations and collector-distributor roadways. While working through the design details, the client was approached with an unsolicited bid for an alternative design: a two-lane system. Given its attractive price point, our team was asked to assess the option and verify its constructability, all within a month. While the option was feasible, it failed to meet essential criteria set by the client — as did the managed lane system.
Vital criteria, as outlined by TxDOT, required lanes not go higher than the deck nor wider than the existing right-of-way, leaving little room for lane additions. Switching directions — and going lower because of height restrictions — our alternative proposal featured a triple stack tunnel through the deck section and a managed lane tunnel to the lake. Though it met the necessary criteria and solved for existing right-of-way constrictions, especially between University of Texas practice fields and an adjacent cemetery, it wasn’t a cost-effective solution. Plus, the required detours and disruptions to local businesses would present excessive prolonged impediments.
After revisiting and revising the necessary criteria, we returned to our original idea of purchasing right-of-way through the deck section, which allowed for a wider footprint where the managed and main lanes could be depressed on the same level below the various cross streets. This plan eased traffic control during construction; reduced the cost of excavation; and eliminated the original alternatives’ required life-safety elements, such as jet fans and escape stairwells. Our design also considered — and solved for — two railroad crossings, one downtown and another in the deck section. To summarize and explain key design aspects, our team developed technical memorandums around airport and rail line configurations and alternatives.
As we moved forward, strategic design configurations emerged as not only viable but also desirable options, providing billions of dollars in cost savings as compared to a tunnel system. Creating and presenting additional alternatives allowed for comparisons to be made regarding mobility, access, environmental effects, safety, implementation and impacts to development. Armed with such valuable information, the client was able to choose the most suitable configuration for the managed lanes.