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Frequently Asked Questions

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What is the Mobility35 Program?

Mobility35 is a regionwide effort to improve mobility and safety along I-35 in Williamson, Travis and Hays counties. Since 2011, the Texas Department of Transportation, the Capital Area Metropolitan Planning Organization, the City of Austin and other regional partners have been working on a plan for improvements to the I-35 corridor.

What is the purpose of the Mobility35 Program?

The purpose of the program is to transform I-35 into a smart and efficient highway. This effort will improve mobility and connectivity for all modes of transportation – cars, transit, trucks, emergency vehicles, pedestrians and bicycles – along and across I-35, as funding is identified.

What are the program limits?

The program limits include 79 miles of I-35 from the Williamson/Bell county line to the Hays/Comal county line.

Who is involved?

Mobility35 is a community-driven effort including local, state and federal agencies, as well as the public and community stakeholders throughout the three-county region. Current partnering agencies are listed on our partnerships webpage.

Why are I-35 improvements needed?

I-35 serves as the backbone of the local, regional and national transportation network. It is also one of the most congested roadways in Texas and has a much higher crash rate than the statewide average for urban interstates. I-35 through Austin is home to five of the 100 most congested roadways according to the Texas A&M Transportation Institute:

  • #1: I-35 from US 290E to SH 71
  • #12: I-35 from SH 71 to Slaughter Lane
  • #34: I-35 from RM 1431 to SH 45N/Louis Henna Boulevard
  • #45: I-35 from Slaughter Lane to SH 45SE
  • #70: I-35 from Parmer Lane to US 290E

A lack of mobility on I-35 threatens the economic livelihood and viability of our cities and state. Not only is traffic congestion inconvenient but it also negatively impacts our quality of life and creates safety issues, delays emergency response times and increases vehicle emissions.

How will the Mobility35 Program make I-35 better?

The Mobility35 Program is transforming I-35 to be smarter and more efficient. Much like the way we communicate has evolved over the last 50 years, so should our transportation system. Consider the evolution of the phone from rotary dial landline to the 1980's cellular brick phone to our modern smart phones. Mobility35 will transform our old, outdated interstate system by doing the following:

  • Adding non-tolled managed lanes in each direction, such as high-occupancy vehicle lanes (HOV), to provide a reliable route for drivers, buses, vanpools and emergency vehicles
  • Incorporating innovative designs, such as intersection bypass lanes, upgraded and innovative intersections, ramp modifications and integrated operations technology
  • Improving safety by increasing the distance for vehicles to enter, exit and change lanes
  • Giving users the ability to make smart choices with regard to how they travel along I-35, such as using managed lanes, enhanced transit, or bicycle and pedestrian accommodations in addition to using traditional general purpose lanes
  • Providing users with up-to-date information using on-road technology to facilitate their decisions about where, when and how they travel
  • Reflecting community values by improving east/west connectivity, maximizing existing right of way without overbuilding, and allowing for technological advancements

What will happen if improvements to I-35 are not implemented?

We can expect our traffic congestion problems to worsen as our population grows. Currently, more than 2 million people live in the Austin area and that number is expected to grow to 3.8 million by 2040.

Who is using I-35?

Despite being an interstate, traffic on I-35 is comprised mostly of local drivers making local trips to and from home, school, work, and other destinations in Central Texas. Daily volumes on I-35 exceed 200,000 vehicles – 86 percent of these vehicles have an origin or destination in Williamson, Travis or Hays counties.

Travelers of I-35 include local and through-traffic, commuters, cross street traffic, transit customers, carpoolers, bicyclists, and pedestrians. Because of the wide array of transportation modes in this corridor, the Mobility35 Program is focusing on effectively moving people along and across the interstate.

Why haven't prior solutions from other plans been implemented?

Previous studies to improve I-35 have focused almost exclusively on large-scale traditional construction projects to address the current and future needs along the corridor. Unfortunately, many of these large-scale projects were determined to be extremely costly and difficult to implement due to the extensive right-of-way acquisitions, construction time required and potential impacts to community. As a result, they have not advanced toward implementation.

What kind of improvements can we expect in the future?

Since 2011, TxDOT has been working with its partners to develop a program that reflects the community's values, which have been shared with us over the last few years. The proposed improvements are smart, efficient and will provide options that let users decide when, where and how to travel.

The Mobility35 Program comprises individual improvement projects along I-35 that collectively provide substantial benefits for congestion relief. The program focuses on innovative solutions to optimize the current facilities and right of way. Improvements will include:

  • Intersection improvements (e.g., diverging diamond intersections, roundabouts and median U-turn intersections)
  • Ramp reversals
  • Modified frontage roads
  • Intersection bypass lanes
  • Extended entrance/exit lanes
  • Bridge reconstruction
  • Traffic Management Systems upgraded to incorporate the latest technologies that provide I-35 users with information they need to make smart decisions
  • Bicycle and pedestrian accommodations

What are operational improvements?

Operational improvements are enhancements or changes to the roadway that do not add capacity, but still contribute to improved traffic flow and efficiency. Some examples of operational improvements include intersection bypass lanes, upgraded and innovative intersections, ramp reversals, increasing entrance and exit lane lengths, and integrated technology.

How do operational improvements help improve traffic flow?

Operational improvements add value to the existing transportation network by making the roadway system more efficient, alleviating traffic congestion and improving safety. For the Mobility35 Program, this all occurs within and by maximizing current right of way. Implementing multiple operational improvements throughout the corridor can substantially reduce travel time and delay. Some examples of operational improvements already constructed that are improving travel times include the diverging diamond intersection at I-35 and RM 1431 in Round Rock and the northbound intersection bypass lane at Parmer Lane.

What lane capacity improvements are proposed?

The proposed improvements include adding more lane capacity along the entire corridor. TxDOT is working with local partners, including Capital Metro, by adding managed lanes along I-35.

Capital Metro has been part of the I-35 planning team since TxDOT began studying ways to enhance mobility along I-35 in 2011. The Mobility35 program would still allow for some transit enhancements. The project team will continue to work with local transit partners.

Right now, public transit buses, registered van pool, and emergency vehicles sit in traffic with all other vehicles on I-35. Managed lanes provide these vehicles with a more reliable route, allowing them to bypass congestion and arrive at their destinations quicker. Where feasible, the Mobility35 program will allow vehicles to directly enter the managed lanes from the frontage road without having to weave through the mainlanes.

What are managed lanes?

Managed lanes are a set of lanes within a highway that are separated from the mainlanes and have operational flexibility to ensure reliability, increase transit use and provide choices to drivers. Examples of different types of managed lanes include HOV lanes, transit-only lanes or special-use lanes. Each of these concepts offer unique benefits and will be evaluated as part of the environmental studies.

What are High-Occupancy Vehicle (HOV) lanes?

An HOV lane, sometimes called a carpool lane, is a special lane reserved for the use of carpools, vanpools and transit vehicles. These lanes are typically located next to the general purpose lanes and enable those who carpool or ride the bus to bypass traffic in the adjacent lanes. Lanes are identified as "2+" or "3+," which refers to the minimum number of occupants to qualify.

What are general purpose lanes?

General purpose lanes are traffic lanes that are available for use by the traveling public and do not have any access restrictions or tolls.

How are the projects being funded?

To date, funding has not been identified for all projects included in the Mobility35 Program. Funding sources could include federal, state, local or private dollars. The needed mobility and safety improvements along I-35 are estimated to cost:

  • Williamson County: $0.9 billion to $1 billion
  • Travis County: $5.8 billion to $6 billion
  • Hays County: $1.2 billion

Current projects are being funded by a mix of voter-approved Proposition 1 funds, Congestion Relief Initiative funds, state gas tax funds and local investments.

What is the schedule and when will improvements happen?

The Mobility35 Program designates where and when the more than 35 projects on I-35 could be built if funding is identified. Several projects currently have funding and construction is already underway.

Construction along the corridor is expected to be ongoing for the next 10 to 15 years. Most projects are funded, and those that are not remain a priority to the region. We will continue to work with our transportation partners and the community to design, develop and construct these projects. For the most up-to date information, visit the Capital Region webpage.

How are projects prioritized?

Several factors are considered when deciding how and when a project moves into the environmental, development or construction phases. When funding becomes available, the program team takes into consideration what phase the project is in, whether additional right of way will be needed, if enough funds are available to complete the project, and the overall impacts of the safety and mobility benefits. These considerations determine the order in which a project advances.

What concepts are being considered for the downtown Austin section of I-35?

The I-35 Capital Express Central project proposes to add two 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 project also includes various operational and safety enhancements that would reconstruct ramps, bridges, and intersections; improve frontage roads; enhance bicycle and pedestrian accommodations and accommodate transit routes. All build alternatives include: 

  • Removing the upper decks on I-35 (between Airport Boulevard and MLK Jr. Boulevard) 
  • Lowering I-35 through downtown (between MLK Jr. Boulevard and Holly Street)
  • Adding two managed lanes in each direction
  • Reconstructing the bridge across Lady Bird Lake
  • Improving bicycle and pedestrian paths 
  • Accommodating current and future CapMetro routes
  • Potentially accommodating a deck plaza in the downtown area funded by others

How will the Mobility35 Program affect the proposed bike pedestrian facilities?

The Mobility35 Program enhances bicycle and pedestrian options. This includes adding shared-use paths on the north and southbound sides of the corridor where sufficient right of way exists, improving east-west connectivity for existing roadway crossings, adding pedestrian signals at all intersections and ensuring pathways are compliant with the Americans with Disabilities Act (ADA).

How can a change in travel improve mobility on I-35?

We all know that it's going to take everything, including the kitchen sink, to manage congestion on I-35. This includes changing the way we get to and from work. TxDOT is contributing to changing driver behavior with the launch of its WorkWise employee work-trip reduction program. WorkWise gives TxDOT employees work options, such as teleworking, compressed work weeks and flexible schedules, as well as encouraging employees to carpool, vanpool, ride transit, and use bicycle and pedestrian accommodations. We must all contribute to working together to change travel behaviors that will help reduce the numbers of cars on I-35.

What is a Traffic Management System?

To transform I-35 into a smart and efficient highway system, we've upgraded our Traffic Management System in the Austin District. The Traffic Management System uses technology to provide I-35 users with information they need to make smart travel decisions and stay safe on the road. TxDOT is adding cameras and large dynamic message signs along I-35 in Williamson, Travis and Hays counties as well as other major roadways in the area, such as US 183, US 290, SH 71, etc. By gathering and disseminating reliable information about what's happening on our roads throughout the day, users will be able to plan their routes based on future traffic patterns and be alerted about lane closures and alternate travel times if they take an express or general purpose lane.

The program also includes the continuation of the Highway Emergency Response Operator, or HERO, safety program. HERO is a free roadside assistance program for stranded motorists that helps keep traffic moving. HERO also responds to emergencies to help with traffic control and debris removal.

How do you plan to address additional noise?

A noise analysis will be conducted as part of the environmental studies required before construction can begin. The analysis considers the current level of noise at many locations throughout the study area, calculates existing and projected future traffic noise levels, and considers noise reduction measures if the predicted future noise levels exceed acceptable levels for properties that surround the project. The result of that analysis will be made available at future public meetings and will be included as part of the environmental study.

Why can't we just move all trucks to SH 130?

A 2013 report by the Texas A&M Transportation Institution entitled "Establishing Mobility Investment Priorities Under TxDOT Rider 42: Long-term Central Texas IH-35 Improvement Scenarios," found that attempts to re-route traffic from I-35 to SH 130 would have limited impact on I-35 congestion. The report cited two reasons for this.

First, much of the truck traffic has an origin or destination near the corridor, making I-35 a desirable or necessary route. Second, truck drivers, traveling through the Austin area without stops generally find I-35 is the most efficient route for their delivery schedule. The report recommended a hybrid approach to solving congestion on I-35 including added capacity, shifting commuter trips to work-at-home jobs, using technology to reduce trips, shifting trips to off-peak periods and increasing alternatives to single occupancy vehicle usage.

It is also important to note that removing tolls from SH 130 would not be free. Investors who contributed private money to pay for the accelerated design and construction would have to be repaid, and that cost would have to be weighed against the cost of improving I-35.

What is a Single-Point Urban Interchange?

A single-point urban interchange (SPUI) is an intersection design that allows a large volume of vehicles to travel through the intersection safely and efficiently by reducing conflict points and the number of traffic signal phases. Similar to a diverging diamond interchange (DDI), the SPUI allows opposing left turns to proceed simultaneously. Unlike a DDI, streams of left-turning traffic in a SPUI are not shifted to the opposite side of the road. Opposing left turns can be made at the same time; with only one set of traffic signals, allowing more vehicles to clear the intersection in one traffic signal cycle.

What are the traffic movements in a SPUI intersection?

The SPUI aligns the left-turn movements of the frontage roads and cross streets opposite one another to form a single intersection at the center of the road. The first movement involves cross street traffic moving through the intersection. The second movement will be opposing left-turn lanes traveling through the same signal from the frontage road onto the cross street. The last movement is for the second set of opposing left-turn lanes traveling from the cross street onto the frontage road. Through traffic on the frontage road is handled via intersection bypass lanes in both directions.

What is a bypass lane?

Bypass lanes are built in-parallel to major highways and provide traffic the opportunity to proceed by bypassing the cross-street intersection, allowing vehicles to avoid the traffic signal. These operational improvements improve mobility by alleviating congestion at cross-street intersections.

What are the benefits?

  • Improved safety: With only one signalized intersection rather than two at a conventional diamond interchange, vehicles only cross paths at one location.
  • Improved travel time: Additional "green time" at traffic signals allows more vehicles to pass through the intersection.
  • Wider turns for large vehicles.
  • Reduced right-of-way requirements.

Are there any travel time enhancements?

Yes. Conventional intersections at highway cross streets use four traffic signal phases. A SPUI only uses three phases, cutting traffic delays at stop lights.

What is a signal phase?

A signal "phase" is the green time assigned to a specified movement or collection of movements in a traffic signal cycle. In other words, when the signal is green for a specific movement (straight through, left turn, etc.), that's a signal phase. When it changes to red and another movement gets a green signal, that's another phase. The complete rotation through all of the phases is a cycle.

Have SPUIs been built anywhere else in Texas?

Yes. There are three SPUIs in north Texas (Plano, McKinney, and Frisco) and one is currently being built in San Antonio.

How can I provide feedback?

The project team continues to take comments from the public. Individual projects will have public events where stakeholders will be able to review proposed improvements, speak with the project team, and submit comments. More information can be found through the Capital Region webpage.

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