Rolling a perfect score

Aug. 18, 2003

Imagine sitting in front of your computer, playing a video game and calling it "work." Sound too good to be true? It might not be. A group of researchers at the University of Washington are working on a first-generation 3-D hot-mix asphalt (HMA) compaction trainer called the Xpactor. The Xpactor works like a video game and allows users to operate a virtual HMA roller in a three-dimensional computer environment.

Imagine sitting in front of your computer, playing a video game and calling it "work." Sound too good to be true? It might not be. A group of researchers at the University of Washington are working on a first-generation 3-D hot-mix asphalt (HMA) compaction trainer called the Xpactor. The Xpactor works like a video game and allows users to operate a virtual HMA roller in a three-dimensional computer environment. The Xpactor can assist learning with any number of compaction issues including proper rolling patterns, longitudinal joint rolling and time available for compaction.

The Xpactor team is led by professors Joe Mahoney and George Turkiyyah and funded by Transportation Northwest (TransNow), a U.S. DOT-funded university transportation center.

The original concept sprang from the idea that the computer gaming world had some valuable insights into what entertains and engages people that could be used to make training more effective and entertaining. The Xpactor's virtual training environment allows users to interact with a simulated construction environment and experience real-time feedback based on their actions. By being immersed in the experience, rather than just being told about it, learning can be more intensive and also longer-lasting. 

Virtual training environments like the Xpactor have been proven successful and are already being used in other fields. For instance, flight simulators are routinely used to train pilots before they move to actual planes, and surgical simulators are often used to train arthroscopic surgeons before they work on real patients.

Xpactor development represents a unique combination of needs and skills. First, it marries a basic industry need of operator and personnel training with a basic academic need of creating more interactive and entertaining environments for learning. Second, it combines the skills of experts in both paving and computer animation.

The result is a simulation designed to help teach basic rolling principles, techniques and considerations. It is applicable to a broad range of users from equipment operators to inspectors to supervisors to project engineers to students. One key industry advantage is that the Xpactor can provide valuable introductory training without tying up expensive equipment time: users can learn the basics or they can experiment with new and different techniques before they ever arrive at the jobsite.

PC drive time

The Xpactor virtual roller can be installed on most current PCs with a capable graphics card. Once started, users or instructors have the ability to set their own paving conditions including pavement thickness, weather conditions, mix type and location using a program interface with MultiCool, a mat cooling software program developed at the University of Minnesota. 

Once the simulation is started, users "drive" their roller over a freshly placed mat. Statistics such as the percent of the mat compacted, the environmental conditions and the time available for compaction are displayed in the upper left corner of the screen, while the upper right corner keeps track of the current mat temperature using a color-coded plan view of the mat. As users drive the roller over the mat, the mat changes colors to reflect the number of roller passes. Users can select other views of the roller like a top view, rear perspective and driver's seat perspective to monitor their progress from different angles.

Teacher's aid

So how do people learn about HMA compaction by using the Xpactor? The Xpactor's strength is that it provides an easy-to-use interface that emphasizes basic compaction principles and techniques that are applicable in almost any situation. Rather than take the place of an instructor, the Xpactor is designed to be used as an instructional tool. 

Although the original concept was to make a product that could teach compaction completely on its own, the design concept evolved into one that was more focused on providing a functional training tool for instructors. The main function of the Xpactor, then, is to provide a venue for teaching compaction. 

"Think of a car racing game . . . although it doesn't necessarily teach people how to drive, it does provide a venue for driving," said Mahoney. "The role of an informed trainer is still critical." 

With the Xpactor, the instructor can set the paving conditions and then coach the students through the proper techniques and strategy. This way, the Xpactor can work in just about any training situation.

For instance, one Xpactor feature allows the user to roll a newly paved lane adjacent to an existing lane; a situation that allows instruction in longitudinal joint rolling technique. Another feature, the color-coded mat, allows users to monitor their rolling pattern and ensure they compact all portions of the mat equally. The Xpactor also can help address one of the more important issues in HMA compaction: the amount of time available for compaction. This is the time it takes for the HMA to cool from placement temperature (typically 275-325°F) to a temperature at which it becomes too stiff to compact (around 175°F). If the rollers aren't finished before the mat stiffens up, the result is often a poor pavement that fails prematurely. In the field it can be difficult to get a feel for how the mat is cooling and how much time is available for compaction. The Xpactor graphically shows mat cooling, the total time available for compaction and the current elapsed time.

Good with children

The Xpactor has been making the rounds at recent industry events including World of Asphalt 2003 and the National Asphalt Pavement Association's (NAPA) 2003 annual meeting. 

"The response to date among equipment manufacturers and state DOT people has been very positive; they feel it can become a viable training tool," said Mahoney. 

Although it was developed for industry and academic training, it seems the Xpactor also can be used to generate interest in paving and engineering. 

The Xpactor was featured at a recent University of Washington engineering open house, which was attended by kids of all ages. Interestingly, younger children often took an immediate interest in the Xpactor over other display items because they could, by themselves, start up the Xpactor and make things happen. In an age where engineering and construction must compete with computer programming and biotechnology for its future work force, this kind of early interest can be very important.

Go to this site

As it stands now, the Xpactor is only the tip of the iceberg. The potential of computer-generated virtual training environments is almost limitless. 

Future Xpactor enhancements will expand the capabilities of the current system and work toward creating an entire virtual HMA paving construction site. Multiple users could then interact with one another via computer networking and assume a variety of roles including paver operator, multiple roller operators, site foreman and even public motorist. The virtual site would be configurable to present users with a rich set of construction projects (such as paving different geometries (like multilane, curved and inclined roads), paving conditions (such as cold weather and nighttime visibility) and traffic patterns.

Computers can and have been used to create truly spectacular, immersive and entertaining virtual experiences. But these types of experiences need not be the exclusive domain of games; there also is a place for education and training. It may not be too long before you, with Xpactor CD in hand, can bump your child from the family Xbox for a little session of "training"--21st century style.

The Xpactor is available for free download at TransNow's website ( Click on the "What's New" button.

The current Xpactor is a beta version. You will need a capable computer (Pentium IV preferred) running Windows XP and a capable graphics card to run the Xpactor. As development continues, the Xpactor will be improved to run on a much wider variety of computers and operating systems.

About The Author: Muench is a graduate student, Civil Engineering, at the University of Washington, Seattle, Wash.

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