Frequently Asked Questions

The I-35 Capital Express Program proposes mobility and safety improvements along 28 miles of I-35 through Austin, from SH 45 North to SH 45 Southeast. It is made up of three, stand-alone projects — North, Central and South. The I-35 Capital Express Program is part of the TxDOT Austin District’s Mobility35 Program, which is composed of improvements to 79 miles of I-35 through Travis, Hays and Williamson counties.

The North project proposes to add one non-tolled managed lane in each direction along I-35 from SH 45 North to US 290 East. The Central project proposes to add two non-tolled managed lanes in each direction along I-35 from US 290 East to SH 71/Ben White Boulevard, with additional flyovers at I-35 and US 290 East. The South project proposes to add two non-tolled managed lanes in each direction along I-35 from SH 71/Ben White Boulevard to SH 45 Southeast. The projects also include operational and safety improvements to the overall roadway, such as extending entrance and exit ramps, building intersection bypass lanes, improving frontage roads and adding or improving bicycle and pedestrian paths.

TxDOT has identified three preliminary build alternatives based on known corridor constraints. Each build alternative proposes to lower the mainlanes and lower or tunnel the managed lanes throughout sections of the project, including downtown.

By 2045, the population in the Austin region is expected to double, which means congestion will continue to worsen unless we do something about it. Daily commuters in Austin experience 66 hours of delay per year on average, according to the Texas A&M Transportation Institute 2019 Mobility Report. What’s more, congestion costs the average Austin commuter $1,269 every year in excess fuel consumption and delays. Congestion is also bad for the environment. The Austin metro area experienced a 178% increase in emissions from passenger and freight traffic between 1990 and 2017, based on data from the Boston Database of Road Transportation Emissions.

TxDOT manages federal and state roadway investments in I-35 and is responsible for working with the Federal Highway Administration to make the decisions about how that funding is spent. However, these decisions are not made in a vacuum, and TxDOT relies on public input as well as coordination with federal, state and local agencies to inform the design of the project. Thousands of people have already provided input on the various concepts over the past 10 years, and this feedback will be considered as the projects progress.

The community has multiple opportunities to provide feedback throughout the environmental and design process for each of the projects. Learn more about input opportunities on our events page at My35CapEx.com. If you have comments or questions, email My35CapEx@txdot.gov or call (512) 366-3229.

Construction of the North and South projects is anticipated to begin in 2022. Construction on the Central project is anticipated to begin in late 2025.

Construction of the North and South projects is anticipated to take three to four years. Construction duration of the Central project is contingent on the environmental study and final design.

Construction can be disruptive. TxDOT will establish construction and traffic control plans to minimize disruption as much as possible. TxDOT already uses advanced traffic management technologies to improve communications with the traveling public. For example, staff monitors delays and provide real-time feedback to contractors to avoid unnecessary delays.

Managed lanes are a set of lanes within a highway that are separated from the mainlanes, and access is controlled by placing restrictions on use. They are designed to provide a less congested route than adjacent general-purpose lanes during peak periods for qualifying vehicles. Examples of different types of managed lanes include non-tolled high-occupancy vehicle (HOV) lanes, transit-only lanes or special-use lanes.

A high-occupancy vehicle (HOV) lane, sometimes called carpool lanes, is a type of managed lane reserved for the use of carpools, vanpools and transit vehicles. HOV lanes save time for car-poolers and transit riders by enabling them to bypass traffic.

One of the goals of the Mobility35 Program is to limit right-of-way impacts. Constructing two lanes in each direction north of US 290 would significantly impact properties along I-35 in highly constrained areas and would impact the I-35 interchanges with US 290 and US 183, which would add more cost to the North project.

Construction of the North project is anticipated to cost approximately $400 million, while construction of the South project is anticipated to cost approximately $300 million. Construction of the Central project is anticipated to cost approximately $4.9 billion. These construction costs are estimates and are subject to change as the projects progress through the environmental study and design phase.

The Central project proposes extensive improvements in a highly constrained urban area. Additionally, the Central project poses unique constructability challenges related to adding the necessary capacity and working within the downtown area, that increase the construction timeline and cost. These factors introduce complexities that are not as present in the North and South projects. The estimated costs are subject to change as the projects progress through the environmental study and design process.

The North, Central and South projects are funded with state and federal gas and tax money. All three projects are high-priority projects and include Texas Clear Lanes funding. Learn more about Texas Clear Lanes at www.dot.state.tx.us/TexasClearLanes.

TxDOT has determined that there are three distinct improvement projects — North, Central and South — with different needs, project characteristics, and potentially serving travelers with different destinations. The National Environmental Policy Act (NEPA) requires that the significance of a project’s environmental impact be evaluated. TxDOT is conducting an Environmental Assessment on the North and South projects. TxDOT is conducting an Environmental Impact Statement on the Central project. Each project is undergoing rigorous environmental study, which evaluates impacts to the human and natural environment, including but not limited to, traffic noise, the community, natural resources, cultural resources and hazardous material sites.

Environmental Assessments and Environmental Impact Statements are two different classifications of documentation and analysis required by the National Environmental Policy Act. An Environmental Assessment determines whether a proposed project has the potential to cause significant environmental effects. An Environmental Impact Statement is prepared when it is anticipated that a proposed project may significantly affect the quality of the human environment. The regulatory requirements for an Environmental Impact Statement are more detailed and rigorous than the requirements for an Environmental Assessment.

TxDOT’s goal is to construct the proposed improvements within the existing state right of way. However, the constrained I-35 corridor presents significant challenges and therefore optimizing the roadway footprint is necessary. As a result, it is anticipated that some additional right of way will be required.

Studies conducted in 2013 and 2015 by the Texas A&M Transportation Institute concluded that re-routing truck traffic from I-35 to SH 130 would have a limited impact on I-35 congestion. Only 14% of I-35 traffic volume is vehicles traveling through the region without stopping. Of that volume, only 1 percent are trucks; the other 86% of vehicles are local I-35 travelers. Additionally, most of the truck traffic on I-35 has an origin or destination near the corridor, meaning that I-35 is a desirable or necessary route.

Right now, public transit buses, registered van pools, and emergency vehicles sit in traffic with all other vehicles on I-35. Managed lanes would help manage overall traffic demand and provide qualifying vehicles with a more reliable route, allowing them to bypass congestion and arrive at their destinations quicker. Where feasible, the North, Central and South projects will allow transit vehicles to directly enter the managed lanes from the frontage road without having to weave through the mainlanes.

The North, Central and South projects improve bicycle and pedestrian accessibility by including shared-use paths on the east and west sides of the corridor. The projects also propose improving east-west connections for existing roadway crossings, adding pedestrian signals at all intersections and ensuring pathways are compliant with the Americans with Disabilities Act (ADA).

A diverging diamond interchange, or DDI, is an innovative intersection design that addresses congestion by allowing vehicles to travel more quickly through an intersection. It also improves safety by reducing the potential conflict points. A DDI is proposed for I-35 at Wells Branch Parkway.

TxDOT is analyzing the feasibility of four design options. Design options affect only a certain segment of the corridor and may be applied to the alternatives, where feasible. One of the design options is local enhancements, which could include deck plazas, or caps. The three build alternatives are being evaluated for their ability to accommodate local enhancements, and TxDOT is working closely with the City of Austin, which is leading the conceptual analysis of caps. These local enhancements would be funded by others.

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Ongoing stakeholder involvement is necessary to support and shape solutions for the corridor. Questions and comments are welcome at any time.

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