FAQs

The I-35 Capital Express Program will enhance safety and improve mobility 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 will add one non-tolled managed lane in each direction along I-35 from SH 45 North to US 290 East. The Central project will add two non-tolled managed lanes in each direction along I-35 from US 290 East to SH 71/Ben White Boulevard. The South project will 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. 

The Central project will lower I-35 through downtown (between Martin Luther King Jr. Boulevard and Holly Street). 

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. 

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 establishes 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. 

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 each phase of the project goes under contract for construction. 

The Central project will include more 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, which increase the construction timeline and cost. These factors introduce complexities that are not as present in the North and South projects. 

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. 

The projects will 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. Transit will have access to the managed lanes, which help manage overall traffic demand and provide a more reliable route, allowing transit to bypass congestion and arrive at their destinations more quickly. 

Enhanced, continuous bicycle and pedestrian paths in both directions along I-35 are included in the design. 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. Several new bicycle-pedestrian-only crossings will be built throughout the corridor.

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 has been working closely with both the City of Austin and University of Texas on the conceptual design of deck caps and stitches along the project corridor. The City of Austin and UT will determine locations for TxDOT to accommodate deck caps and will also fund operations and maintenance of these enhancements throughout the life of the project. TxDOT will be responsible for building the infrastructure and implementing fire suppression requirements during construction. 

Current frontage road posted speeds within the project area range between 40-50 mph. Posted speeds are determined once construction is complete. 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. 

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.
• Reconstructing east-west crossings at: Airport Boulevard, Wilshire Boulevard, 38 1/2 Street, 32nd Street, Dean Keeton Street, and Manor Road, 15th, 12th, 11th, 7th, 6th, 5th, 4th, and Cesar Chavez Streets. 
• Existing east-west crossings will be widened and enhanced; new bicycle-pedestrian crossings will be constructed at 4th Street, 51st Street, Red Line at Airport Boulevard and Lady Bird Lake. 
• Additional bicycle-pedestrian crossings include 3rd Street, 15th Street and 41st Street. 

The Central project will 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 various east-west crossings, including south of Airport Boulevard, 4th Street and Riverside Drive. 

TxDOT, in coordination with the City of Austin and University of Texas, 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 Airport Boulevard to 38th 1/2 Street, Manor Road to Martin Luther King Jr. Boulevard, 12th Street to 11th Street, and 7th Street to Cesar Chavez Street. 

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.