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. All proposed build alternatives include removing the upper decks and lowering lanes through the project corridor, 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 South project broke ground in October 2022 and the North project broke ground in March 2023. The Central project is expected to begin construction in 2024.
Construction of the North and South projects is anticipated to take six years. Construction duration of the Central project is anticipated to take six to eight years.
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.
The construction cost of the North project is $606 million, while the construction cost of the South project is $548 million. Construction of the Central project is anticipated to cost approximately $4.5 billion. Central construction costs are estimates and are subject to change as the project progresses 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 conducted 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.
The project team has considered and documented community input regarding rerouting traffic from I-35 or redesignating I-35 to SH 130. Every day, more than 200,000 vehicles travel on I-35 within the project area (from US 190 East to SH 71/Ben White Boulevard). Of this amount, 82% is local traffic, meaning it originates or ends in the vicinity of the project area. Through traffic, or traffic that does not start or stop within the project area, comprises 18% of total traffic. With regard to truck traffic, even if there were no trucks that used I-35, the same number of lanes would be required to manage current and future demand. In addition, incentives to use SH 130 would have little effect on trucks needing to make deliveries along the I-35 corridor.
SH 130 is part of the Central Texas Turnpike System (CTTS), which is made up of segments from SH 130, SH 45 North, Loop 1 and SH 45 SE. An outstanding $3 billion in debt is assigned to the system which would also be the cost to remove the tolls on SH 130. The current $4.9 billion allotted for the I-35 Capital Express Central project would not be eligible for paying this outstanding debt. TxDOT would need a waiver to reduce or remove the tolls. While this can happen, it is usually for a temporary scenario such as construction.
Each alternative was measured for its ability to accommodate Capital Metro’s Project Connect proposed light rail system at east-west crossings. Currently public transit buses, registered van pools and emergency vehicles must remain 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 more quickly.
Transit would have access to the managed lanes in the proposed build alternatives, which could improve overall TxDOT is collaborating with CapMetro to study the feasibility of direct transit access and identify funding sources.
Enhanced, continuous bicycle and pedestrian paths in both directions along I-35 are included in the proposed build alternatives. Additional improvements include: 16.6 miles of shared-use paths in construction or design, 13 connections to the urban trail network and bicycle network, and more than 28 intersections that contain bypass lanes to reduce through traffic and create safer areas for people walking, biking, or otherwise not in vehicles.
Further, based on input from community groups, including Downtown Austin Alliance, Reconnect Austin and Rethink35, each east-west crossing within the project area has been enhanced to include wider bridge structures with 30 feet of combined shared-use path and buffer between bicyclists and pedestrians and vehicular travel lanes for a safer, more user-friendly experience. Among the recent design changes included in the proposed build alternatives are several new bicycle-pedestrian-only crossings throughout the corridor.
For illustrations on the bike/ped safety concept, visit: https://my35capex.com/bicycle-pedestrian-improvements/
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 working closely with the City of Austin and the University of Texas on the analysis of deck plazas or caps and other local enhancements. Eight potential deck plazas or up to 33 acres of caps have been identified.
During construction, TxDOT will be responsible for building the infrastructure and implementing fire suppression requirements.
The City and UT will also fund operations and maintenance of the surface-level enhancements throughout the life of the project.
TxDOT has conducted a greenhouse gas (GHG) analysis for the statewide on-road transportation system and associated motor vehicle emissions and published the Statewide On-Road Greenhouse Gas Emissions Analysis and Climate Change Assessment technical report. This report also discloses projected climate change projections for the state of Texas, how TxDOT is responding to a changing climate and TxDOT actions and funding that reduce on-road GHG emissions. A brief summary of this report will be incorporated in the Environmental Impact Statement (EIS).
Potential impacts on the human and natural environment that would result from the proposed build alternatives and no-build alternative will also be evaluated as part of the EIS process. The outcome of these studies and the identification of the preferred alternative included in the Draft EIS will be presented to the public and agencies at the public hearing. Topics include water resources, air quality, traffic noise, community impacts, vegetation and wildlife, threatened and endangered species, indirect and cumulative Impacts, historical and archeological resources, hazardous material sites, land use, parkland and climate change.
Current frontage road posted speeds within the project area range between 40-50 mph. Posted speeds are determined once construction is complete. For all proposed build alternatives, TxDOT is lowering frontage road design speeds to 35-40 mph.
TxDOT routinely evaluates the design guidance, which includes design speed, and must comply with federal and state standards for highway design, including TxDOT’s Roadway Design Manual, the AASHTO Policy on Geometric Design of Highways and Streets and the Texas Manual of Uniform Traffic Control Devices.
Design speed is used explicitly for determining minimum values for road design, such as horizontal curve radius and sight distance based on the roadway function and classification. Roadway geometric design features such as cross-section elements, lane widths, shoulder width, etc., are determined based on the road function and safety in relation to the design speed.
The posted speed limit is normally set at the nearest value to the 85th percentile speed ending in five or zero of the observed speed of a group of vehicles traveling on a section of road. City governments and TxDOT must conduct traffic and engineering studies according to requirements outlined in TxDOT’s publication, Procedures for Establishing Speed Zones, when setting a speed limit on the state highway system.
TxDOT is improving east-west connectivity by rebuilding cross street bridges for wider, safer bicycle and pedestrian crossings. These proposed crossings include:
- Thirty feet of combined shared-use paths and buffers between the road and the paths.
- A street and shared-use path connection at 5th street.
- New bicycle-pedestrian bridges between US 290 East and 51st Street, at both Red Line crossings at Airport Boulevard and 4th Street, and other potential locations.
Each alternative was evaluated on its ability to provide enhanced vehicular, bicycle and pedestrian east-west crossings along the I-35 Capital Express Central project limits, as well as its ability to accommodate Capital Metro’s Project Connect proposed light rail system at east-west crossings.
TxDOT, in coordination with the City of Austin, is evaluating multiple deck cap areas that were recommended as potential green spaces within the urban core of Austin. The deck plazas will also improve east-west connectivity. The locations were recommended from 12th Street to 11th Street, 8th Street to 6th Street and 4th Street to Cesar Chavez Street as well as an enhanced cap area at Dean Keeton Street near The University of Texas.
TxDOT is evaluating multimodal enhancements to east-west crossings including wider and more accessible cross streets at multiple locations. TxDOT is also coordinating with the City of Austin to tie into the city street network as well as the Butler Hike and Bike Trail at Lady Bird Lake for continuity of bicycle and pedestrian accommodations.
To celebrate Austin’s cultural and community diversity, TxDOT has launched Live35, an aesthetic design program in partnership with the City of Austin for the I-35 Capital Express Central project. The goal is to gain community input to help identify design elements that create an I-35 with cross streets and east-west connections that resonate with Austinites. This will improve east-west connectivity and enhance bridges and intersections to reflect the Austin community. TxDOT will also work with the community to develop materials and gather feedback on outreach and engagement strategies.
TxDOT is evaluating existing and future traffic noise impacts and ways to reduce them (by implementing noise barriers) as part of the Draft Environmental Impact Statement (EIS). The results of this study, including proposed noise barriers, will be included in the Draft EIS and presented at the public hearing.
For more information, please refer to the traffic noise barrier brochure: https://ftp.txdot.gov/pub/txdot-info/env/toolkit/730-01-bro.pdf
Section 4(f) are regulations that say the Federal Highway Administration and DOT agencies like TxDOT can only approve the use of land from publicly owned parks, recreational areas, wildlife and waterfowl refuges, or public and private historical sites once certain criteria has been met.
Section 6(f) are regulations that say that property acquired or developed through assistance from the Land and Water Conservation Fund Act (LWCF Act) cannot be converted to a non-recreational site without the approval of the US Department of Interior’s National Park Service.
Ongoing stakeholder involvement is necessary to support and shape solutions for the corridor. Questions and comments are welcome at any time.Contact Us