Traffic congestion is as familiar as bluebonnets on the roadside for anyone who’s traveled I-35 in the last 20 years.

The interstate route — which in Texas stretches south from the Red River all the way to the Rio Grande at Laredo — has carried commerce and commuters across the Lone Star State for nearly 150 years. Before the modern highway was christened I-35 in 1959, much of it was known as the Chisholm Trail.

Once crowded with cattle in long drives north to Kansas, today’s I-35 has a similar reputation for being tightly packed — only now it’s bumpers, not bovines, causing the slowdown. In an innovative approach to improving the roadway’s capacity, the Texas Department of Transportation (TxDOT) created MY 35, a citizen-driven effort to expand a 96-mile stretch from Hillsboro to Salado of I-35 in the Waco District. At an estimated total cost of $2.5 billion, the overall effort is made up of 17 smaller construction projects and targeted for completion in 2017.

TxDOT Teams with TTI

Commuters and businesses alike will soon benefit from the expansion of I-35 in TxDOT’s Waco District. Due for completion in 2017, the project is widening corridor capacity and improving safety to better meet the traveling needs of Texans.

A project of this size is a huge undertaking, and not just when it comes to coordinating the construction itself. TxDOT is reconstructing nearly 100 miles of roadway in a relatively short amount of time, and that affects hundreds of thousands of citizens living nearby, tens of thousands of businesses, and millions of travelers over the life of the project.

TxDOT engaged the Texas A&M Transportation Institute (TTI) to provide independent technical support for the effort. One way TTI is helping is by providing mobility coordinators to keep citizen groups and businesses informed and lessen any negative impact of construction.

For example, TxDOT is converting many two-way access roads along the interstate to one way to improve safety. To business owners situated beside I-35, the change can seem threatening because, in the short term at least, it potentially changes customer access to their stores.

“Our job is to talk through the entire process with the business owner,” says TTI Research Engineer Jim Dale, lead mobility coordinator on the project. “We let them know we understand their concerns and help them see the longer-term benefits of the changes.”

Helping TxDOT get the word out is one of two major jobs for TTI on the project. The Institute developed a communications plan for the department and has done everything from designing flyers, truck stop signs and email alerts to organizing public meetings and writing, editing and distributing My 35 Central Texas News, a monthly newsletter aimed at keeping interested parties informed.

“Whatever means we use, our main goal is to get information into the hands of citizens and business owners so they can make the best decisions possible for their travel needs,” says Dale. “And very soon we’ll be getting the word out in a whole new way.”

Getting the Word Out in Real Time

http://my35.org

What Dale is referring to is a first-of-its-kind traveler-information system developed by TTI for the I-35 project. The system integrates several methods for capturing data, forecasts congestion along the construction route, and provides that information to everyone who wants it. The system, currently being refined, is a primary example of how TxDOT and TTI are working together to improve transportation in Texas.

“The purpose of the system is two-fold,” explains TTI Research Scientist Bob Brydia, principal investigator on the traveler-information project. “First, it’ll give reliable traffic forecasts for I-35 travelers while the expansion project is under construction. Second, after construction is finished, it’ll form the basis for a comprehensive traffic management system for TxDOT’s Waco District.”

The traveler-information system is similar in concept to modern traffic management systems used in urban areas. The unique aspect is combining construction data and corridor travel data for a long interstate highway passing through rural and urban areas. Put simply, the system marries three data-gathering methods together to create reliable forecasts for travelers:

1. Bluetooth® technology — Travelers’ devices (e.g., cell phones, laptops and the GPS systems in newer cars) are anonymously pinged at point A and point B, giving a reliable estimate of travel time between the points.
2. Wavetronix sensors — Placed strategically along the corridor at 17 points of high traffic interaction, such as where a state highway crosses I-35, these sensors capture traffic volume.
3. End-of-queue warning systems — Radar detectors mounted in orange barrels around work zones measure speeds of approaching vehicles as they near the work zone, and patterns of slowing traffic (indicating a backup in traffic flow) are noted.

TTI has developed computer algorithms to integrate this information together to create reliable traffic forecasts, which are then passed on to travelers. Once the system is fully up and running, travelers will be able to access reliable forecasts via the Internet of what traffic on I-35 in Waco will be in an hour, before they ever leave Hillsboro, some 40 miles away.

It sounds simple enough in theory, but gathering and analyzing the data and creating reliable forecasts are incredibly complex tasks. And different information systems have to talk effectively with one another to make sure the information stays accurate and useful by the time it reaches travelers.

“From our perspective, a real success story of this project is how effectively we’ve been able to interface with TxDOT’s LoneStar traffic management system,” says Brydia. “Using their data protocols, we feed our information to them, and that helps drive the messages you see on the portable changeable message signs [PCMSs].” PCMSs display traffic forecasts along the roadway.

While congestion can be inconvenient for travelers, it can also be costly — in very real terms — for big business. Knowing where work zones are, what lanes will be closed, and when to expect slower travel is vital for companies like Walmart and H-E-B. They rely on I-35 to get their goods via truck from major distribution hubs to their brick-and-mortar stores. When you’re talking perishables, traffic backups can mean the difference between fresh and spoiled milk — and that can translate into lost revenue for the company and higher prices for consumers.

Similarly, with better information on hand, emergency management services personnel can get to the scene of an accident sooner. The life-saving potential there really needs no further explanation.

“Right now, the main way for alerting travelers is via PCMSs and daily email alerts,” explains Brydia. “Very soon we hope to take advantage of social media, including Twitter, and supply real-time information to TxDOT’s My35.org website in the form of a dynamic traffic map.”

Jodi Wheatley, Waco District’s information specialist for the project, acknowledges that without TTI’s help, the I-35 expansion effort would have been much tougher.

“Reconstructing almost 100 miles of interstate is a massive job for the department, and at the end of the day we at TxDOT want to be as responsive and helpful as we can to our fellow Texans,” Wheatley says. “Because of the scope of the project, that would be much more difficult without TTI’s logistical support and technical know-how. Maybe even impossible.”

The final mat of SMA thin asphalt overlay on SH 6 access road in Bryan, Texas.

Tom Scullion, manager of TTI’s Flexible Pavements Program, and Cindy Estakhri, manager of TTI’s Recyclable Materials Program, are working with the Texas Department of Transportation (TxDOT) to implement the use of three new thin asphalt mixes: a crack-attenuating mix (CAM), fine-graded stone matrix asphalt (SMA) and permeable friction course (PFC).

The goal of the research was to develop mixes that help to reduce costs by using a very thin overlay while retaining quality. The research results indicate that the use of good-quality Grade 5 aggregate is one of the keys. “To place it thin, you need a smaller rock. Grade 5 aggregate is in abundant supply and is almost a waste product at some quarries. We felt we could obtain the Grade 5 aggregate at a reasonable cost,” Estakhri notes.

Researchers wanted mixes that were easy for maintenance personnel to work with, very thin and easy to compact. To ensure the good quality of these mixes, all three of them have to pass the rutting (Hamburg wheel tracking test) and reflection cracking (overlay tester) performance tests.

The CAM mix was not originally intended to be a surface mix. The first purpose for this asphalt-rich mix was as a thin treatment below the surface to retard reflective cracking. In an early project in Houston, a CAM was placed on a high-volume interstate highway and left exposed to traffic for over one year. It performed very well, leading to its modification for use as a thin overlay for surface use. When used as a thin overlay, it’s known as a fine dense-graded mix (DGM) instead of a CAM. By lowering the target density to 96.5 percent, the new DGM has between 0.7 percent and 1.0 percent less asphalt than the original CAM.

Three quarters of an inch of PFC thin asphalt overlay on US 183 south of Breckenridge, Texas, in Stephens County.

The fine-graded PFC was developed as an alternative to seal coat on lower-volume roadways. It drains well and has good friction characteristics. An added benefit is reduced noise compared to seal coats. Estakhri notes that “sometimes people complain about the noise associated with seal coats. Because PFC is finer, it makes for a quieter surface.”

Sarah Horner, assistant area engineer with TxDOT’s Brownwood District, oversaw the recent use of the fine-graded PFC on US 183 in Stephens County. The PFC was laid three quarters of an inch thick in both travel lanes. TxDOT hopes to combat a bleeding issue that compromised the existing surface. (Bleeding occurs when too much asphalt squeezes out on top of the aggregate, and this causes a slick surface.)

Sarah Horner, assistant area engineer with TxDOT’s Brownwood District, performs a test on the new PFC surface on US 183 south of Breckenridge, Texas.

“We’re hoping that the open PFC will allow the bleeding to go up into the PFC and keep it away from traffic. We’re also hoping for a smoother, quieter ride,” Horner says. They are expecting at least five years with little or no maintenance from the new PFC surface.

The fine-graded SMA has an excellent surface texture, resists rutting, and is useful on roadways with high volume and numerous intersections. Darlene Goehl, materials engineer for TxDOT’s Bryan District, chose SMA for a recent resurfacing project on the access roads for SH 6. Goehl notes, “We can have problems with seal coats and turning movements. Seal coats often shove [or ripple, creating a washboard effect] in an intersection. We were looking for a rut-resistant, crack-resistant thin mix that we could place in urban areas. We’re expecting 10 to 12 years of service life from the SMA surface.”

All three of the mixes were created as alternatives to seal coats or multiple inches of hot-mix asphalt. “It’s not as cheap as a seal coat, but it will be cheaper than 2 inches of regular hot mix,” says Estakhri. “Currently those are the alternatives. These mixes are in between those options. Even though they are much thinner, we think that these overlay mixes will perform better than 2 inches of hot-mix asphalt.”

Estakhri notes that TxDOT is incorporating these new mixes into its specifications. “Texas has such a huge network of roads to maintain, some in remote areas. TxDOT has to be more creative in terms of extending its dollars to cover more area,” she says.

Sustainability — a popular, emerging concept — has become a key consideration in the delivery and operation of transportation infrastructure, and at all levels of government. Sustainability deals with meeting human needs in the present and future, while preserving and restoring the environment, fostering community health and vitality, promoting economic development and prosperity, and ensuring equity among population groups and over generations.

“At this time of fiscal constraint, the New York State Department of Transportation [NYSDOT] must make some tough choices. To guide our decisions, we have incorporated the ‘triple bottom line’ of economic competitiveness, social equity and environmental stewardship into our programming and investment guidance. NCHRP’s A Guidebook for Sustainability Performance Measurement for Transportation Agencies provided NYSDOT with a much-needed methodology and comprehensive list to develop our sustainability performance measures.”
Debra Nelson,
NYSDOT assistant to the director of operations

“Sustainability is a way of looking at other costs that don’t always get considered in the decision-making process. Thinking about these costs should be broader than just the tangible dollars,” says Tara Ramani, assistant research scientist with the Texas Transportation Institute (TTI). “The question is less ‘how can we implement sustainable transportation?’ but really more ‘how can transportation support the principles of sustainability?’”

Ramani, along with the international team led by Joe Zietsman, head of TTI’s Environment and Air Quality Division, produced a sustainability guidebook that teaches transportation practitioners the principles of sustainability, how to develop goals and objectives based on sustainability, and how to apply performance measures for these goals.

A Guidebook for Sustainability Performance Measurement for Transportation Agencies provides a generally applicable framework that transportation agencies can adapt and use, either in their existing performance measurement programs or as a part of a new sustainability initiative. The guidebook provides a practical approach to understanding sustainability, and identifying and applying sustainability-related performance measures. It discusses linkages to an agency’s mission and strategic plan, and the integration of these sustainability measures into other programs and agency business practices. The guidebook also contains a compendium of sustainability performance measures, with a menu of goals, objectives and performance measures that agencies can use as the basis for their performance measurement applications.

Part of the concept of sustainability involves choices: walking, biking, commuting. Making multiple modes work in harmony with environmental needs and economic realities — without losing the human factor from the equation — is the real challenge.

“Working with performance measures can be a daunting task due to the large number of possible measures, extensive data required and complexity involved in applying the measures,” Zietsman said. “Moreover, a first step in developing performance measures for sustainability is to understand what sustainability means, and how it applies to transportation networks, systems, facilities, projects and activities at different stages, scales and time frames.”

The guidebook incorporates real-world examples from departments of transportation and private industry in both the United States and Europe. It’s designed to be flexible so that any division in any agency can apply, refine and modify it based on the specific context for planning, programming, project development, construction, maintenance or operations. The framework can be used in many different ways, such as to evaluate progress, assess current conditions, forecast the future, make decisions or communicate with stakeholders.

“The guidebook provides a wealth of information and resources for departments of transportation to use to understand the concept of sustainability and apply performance measures for their sustainable transportation goals,” Zietsman said.

Published by the National Cooperative Highway Research Program (NCHRP) in November 2011, the guidebook has been well received across the country. Zietsman plans on leading TRB webinars to help transportation officials learn how to use the guidebook.

“This guidebook should be of immediate use to those who are familiar with their own agency’s performance measurement program but need to provide useful information to agency leadership on how effectively their organization is meeting sustainability goals,” said Lori L. Sundstrom, a senior program officer with TRB. “The examples included illustrate how sustainability can be successfully added to an agency’s existing performance measurement system.”

The Texas Transportation Institute (TTI) recently completed a project to examine some of these impacts.

“The purpose of the project was to measure the impact of the increased level of energy-related activities on the Texas Departments of Transportation’s [TxDOT’s] right-of-way and infrastructure, develop recommendations to reduce and manage TxDOT’s exposure and risk resulting from these activities, and develop recommendations for potential changes to business practices,” says Cesar Quiroga, manager of TTI’s Research and Implementation Office in San Antonio, Texas.

“Pavement was a big part of the project for the researchers,” says TxDOT project director Dale Booth. “The researchers focused their efforts in Abilene, Lubbock and the Dallas-Fort Worth area. And they found quite a bit of distress in those areas related to those industries.”

The researchers focused on the infrastructure impact by heavy trucks and machinery moving in and out of oil and gas well sites, as well as wind farms. Some of the problems observed included the following:

• failures,
• surface ripples,
• tire tracks on unpaved shoulders,
• drainage problems at driveways,
• mud tracking,
• alligator cracking,
• shoulder patches,
• cracked seals and
• loss of surface.

The above series of photos shows various types of pavement failures observed during field visits.

The researchers also collected ground-penetrating radar and falling weight deflectometer data. Considering the increasing level of activity in connection with the Eagle Ford Formation in South Texas, the researchers also met with officials from the Laredo, San Antonio and Yoakum TxDOT districts.

“After we gathered the data, we conducted an evaluation of impacts of energy developments on the transportation infrastructure, including pavement impacts and remaining pavement life, roadside impacts, operational and safety impacts, and economic impacts. We also developed file geodatabases of relevant energy- and transportation-related datasets and provided TxDOT with recommendations on how to alleviate potential problems that may arise with energy-related activities,” says Quiroga.

The researchers used these geodatabases to generate a range of reports mapping the following:

• wind farms in relation to other energy developments as well as transportation datasets;
• wind farms, competitive renewable energy zones and transmission lines;
• pipelines in relation to oil and gas wells;
• permitted (and completed) oil and gas wells over time;
• permitted (but not completed) oil and gas wells;
• oversized/overweight routes in relation to energy developments;
• pavement statistics in relation to energy developments over time; and
• crash locations in relation to energy developments.

Key recommendations at the end of the research included the need to maintain the geodatabase of energy developments to help TxDOT forecast and manage future developments, the need to engage and coordinate with energy developers earlier in the process, and the need to strengthen certain protocols and requirements (e.g., those dealing with triaxial design checks, cross-sectional elements on rural two-lane highways, and driveway permits).

“As energy development continues in our state, especially in the gas-bearing shale formations that have become so busy in the last 10 years, having a statistical basis to show their impacts serves as a springboard for additional funding,” says Booth.

Booth also notes the importance of the geodatabase as a communications and predictor tool for TxDOT.

“As a communications tool, it is a visual way to predict well permits and well development in any area. When you run the program year to year, you can see ‘waves’ of wells progressing across the screen,” says Booth. “If you then show your audience the pavement distress and how that has progressed through the years, it paints a vivid picture of what energy developments in our state are doing to our transportation infrastructure. As a communications tool and predictor of future needs, the geodatabase is the centerpiece of this project.”

“We used to be the best at everything,” Rendell said during his speech occurring days before he stepped down as governor. “Now our transportation is mediocre. What happened to us?”

The outspoken and outgoing governor made national headlines the week before when he was critical of an NFL decision to postpone a football game because of an approaching snowstorm. He continued that theme in describing America’s unwillingness to tackle the infrastructure problem.

“How many bridges have to fail — how many levees have to break before we wake up?” Rendell asked.

He said there were numerous ways to raise the money for road-building projects and proposed lifting a ban to allow states to place tolls on previously existing federal highways. “May I be bold enough to suggest it’s time to stop nation building in Iraq and Afghanistan and start nation building in the USA?”

Acknowledging that solutions are ‘fraught with political obstacles,’ Rendell told the crowd he was in favor of toll roads, public-private partnerships and additional taxes in order to improve infrastructure. He also said stimulus funding creates jobs.

Rendell proposed a nationwide public relations campaign to help change the way Americans think about infrastructure and urged those in attendance to educate their neighbors about why it’s important for the economy.

“We can win this fight, and we need you to be one of the soldiers,” he said.

Sen. Glenn Hegar, Jr., chair of the Sunset Advisory Commission; Rep. Drew Darby, chair of the House Select Committee on Transportation Funding; Deirdre Delisi, chair of the Texas Transportation Commission; Representative Eddie Rodriguez, vice chair of the House Select Committee on Transportation Funding; and Rep. Rafael Anchia, member of the Sunset Advisory Commission, participate in a State Transportation Roundtable.

Maintaining the existing highway network is one of the Texas Department of Transportation’s (TxDOT‘s) top priorities. Many segments on important routes have now exceeded their design lives and are in need of major rehabilitation. To assist in this critical task, TxDOT contracted with the Texas Transportation Institute (TTI) to initiate a groundbreaking corridor analysis project. This new interagency agreement will permit TTI engineers to implement the products of many years of research while providing answers to TxDOT districts on the optimal approach to repair these distressed highways.

Researchers took coring samples along I-20 to determine the cause of stripping.

Working with TxDOT engineers, TTI has almost completed the first study on the Interstate 20 corridor in the Odessa District. “The length of the roadway is 165 miles, and it consists of 20 different pavement sections, each with different layer thicknesses and maintenance histories,” says Tom Scullion, the senior research engineer at TTI leading this effort. “The goal of the study is to develop a 10-year pavement rehabilitation plan for each section based on determining the underlying cause of the pavement problems.”

The research team initially conducted a full ground-penetrating radar (GPR) survey. Then after meeting with district personnel to discuss roadway history and priorities, the team executed a falling weight deflectometer test program to evaluate the in situ structural strengths and a verification field-sampling program. For each section, the cause of the distress, the most appropriate repair strategy and the priority of the work were reported to senior district personnel.

“Priority 1 projects were identified as those that have essentially failed and need full rehabilitation in the next 2 years. Priority 4 projects are those judged structurally adequate for the next 10 years,” says Scullion.

This project has generated substantial interest within TxDOT, and work is underway to evaluate three major U.S. routes in the Lubbock District. The team is also about to initiate an evaluation of Interstate 45 in the Bryan District.

An Eye Out for the Environment — Reclaiming Asphalt

In addition to conserving energy and protecting the environment, the use of reclaimed asphalt pavement (RAP) can significantly reduce the cost of asphalt mixes. These mixes continue to increase in cost, so savings benefit operating agencies. A key problem with RAP mixes is variability, which is the main reason why many state departments of transportation, including TxDOT, limit the use of RAP. In most circumstances, RAP variability is closely related to RAP stockpile management and RAP processing.

The use of reclaimed asphalt pavement can significantly reduce the increasing cost of asphalt mixes.

In 2010, TTI developed a set of state-of-the-practice guidelines for TxDOT regarding RAP processing and stockpile management. The principal points were to 1) eliminate contamination of RAP stockpiles, 2) keep RAP stockpiles as separate as possible, 3) blend thoroughly before processing or fractionating the multiple-source RAP stockpiles, 4) avoid over-processing, 5) use good practice when storing the processed RAP, and 6) characterize and number the processed RAP stockpiles.

“When properly designed and constructed, RAP mixes could have the same or similar performance as pure hot-mix asphalt [HMA] mixes,” says TTI Associate Research Engineer Fujie Zhou. “The stockpile management practices and RAP-processing techniques described in this report help TxDOT better control RAP variability.”

Related report: RAP Stockpile Management and Processing in Texas: State of the Practice and Proposed Guidelines, http://tti.tamu.edu/documents/0-6092-1.pdf

New Technologies for Assessing Hot-Mix Asphalt Overlays

HMA overlays are a critical part of TxDOT‘s maintenance program, as are methods to evaluate the quality and uniformity of the overlays. In 2006, TTI began a research project to evaluate several available non-nuclear density gauges and further refinement of infrared imaging and GPR for use in evaluating HMA overlays.

Workers use the second-generation infrared sensor bar on a paving project

The project led to the development of data collection/analysis software and a new infrared sensor bar that is mounted on the back of a paver to provide uniformity in measurement. These technologies provide a much-improved method to collect and analyze HMA-paving projects for uniformity and quality as compared to traditional spot tests.

The technologies assist with the evaluation of segregation on a project, project uniformity and overall project quality. The PAVE-IR system can provide near 100 percent coverage of a paving project. Based upon work completed, the guidelines developed by TTI should serve to flag potentially segregated areas with thermal imaging. A new test procedure, Tx Method 244 F, has been developed by TxDOT, and in 2010, the Pave-IR system was included in the department’s construction specifications. (PAVE-IR is an infrared temperature bar system developed by TTI.)

“Based upon work completed,” Mikhail continues, “the guidelines developed by TTI should serve to flag potentially segregated areas with thermal imaging.”

Related report: New Infrared and Radar Systems for Detecting Segregation in Hot-Mix Asphalt Construction, http://tti.tamu.edu/documents/0-4577-2.pdf

Getting It Right the First Time — Proper Design of Asphalt Overlays

The placement of an asphalt overlay is the most common method used by TxDOT to rehabilitate existing asphalt and concrete pavements. The type of overlay and its required thickness are important decisions that TxDOT engineers make on a daily basis. To perform well, an asphalt overlay must have a balance of both good rut and crack resistance. Furthermore, overlay performance is highly influenced by many factors, such as existing pavement conditions, traffic loading and environmental conditions.

The main screen of the asphalt overlay design and analysis system.

In response to the need, TTI conducted a research project with the objectives to develop 1) an HMA overlay mix design balancing rutting and reflective cracking requirements, 2) guidelines for evaluating existing pavements focusing on identifying repair locations and collecting information needed for the HMA overlay thickness design in which the primary concern is reflective cracking, and 3) an HMA overlay thickness design system focusing on reflective cracking and rutting.

In addition to three published reports, the TTI research team headed by Associate Research Engineer Fujie Zhou conducted several workshops to train TxDOT personnel on the Texas Asphalt Concrete Overlay Design and Analysis System (TxACOL). “We trained more than 30 representatives from TxDOT on how to use TxACOL software,” says TTI Division Head of Materials and Pavements Andrew Wimsatt. “The attendees practiced the software step by step and by the end of day knew how to properly design an asphalt overlay using the program.”

Related report: Mechanistic-Empirical Asphalt Overlay Thickness Design and Analysis System, http://tti.tamu.edu/documents/0-5123-3.pdf

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