Summary of relative contributions of emissions from three European projects

Much of the energy costs of asphalt roads comes at the asphalt plant, where aggregate is dried and mixed with liquid asphalt at high temperatures. The EPA estimates that for every ton of hot-mix produced, an HMA plant will emit 35 pounds of CO2. This means if a given roadway project uses 1,000 tons of asphalt, emissions at the asphalt plant alone will reach 35,000 pounds of CO2. This is roughly equivalent to paving four miles of a four lane highway. One way to cut down on fuel burning is through use of warm-mix asphalt technologies. If we assume that warm-mix uses 20% less energy, these emissions for the same project could be reduced to 28,000 pounds of CO2. This reduction in CO2 is roughly equivalent to taking one car off the road for a year. While this may not seems like a lot on its own, these numbers add up over longer roadway projects and on a global scale.

Overall, the use phase of a roadway is the dominant source of greenhouse gas emissions. However, that doesn’t mean we can’t continue to clean up materials production and roadway construction.  When we consider cleaning up our air, we need to think about not only our cars but the roads they drive on.

For more information on energy use and greenhouse gas emissions in road construction, check out the following links:

Energy Cost of Asphalt and Reinforced Concrete Pavement Materials and Construction

Sustainable Roadway Construction: Energy Consumption and Material Waste Generation of Roadways

Carbon Footprinting on Highway Projects: Examples from Norway, Sweden and UK

Credit from the Greenroads Manual – Lifecycle Inventory

A UW startup company, Pavia Systems is emerging as a big player with growing impact on the roadway industry, nationally and abroad. Pavia is blazing the way in developing Web-based training courses that contractors, government agencies, and equipment manufacturers use to keep employees current on evolving technology and industry best practices to improve roadway construction and safety.

Over the last three years, Pavia’s revenues have grown 53 percent — impressive given how hard the economic recession hit the construction sector.

Pavia emerged from decades of UW research by Joe Mahoney, professor of civil and environmental engineering and one of the nation’s top authorities on paving materials and methods. Colleague Steve Muench, CEE associate professor and paving specialist, contributed his expertise in self-directed learning through multimedia materials.

In 2002 several state transportation departments sought permission to use award-winning online training materials developed by Mahoney, Muench, and George White, a UW engineering graduate and research engineering working in Mahoney’s lab. The UW Center for Commercialization (C4C) assisted them with intellectual property protection and licensing agreements. These early experiences generated a sense of the potential for a more commercial venture down the road.

Full Speed Ahead

George White periodically talked about entrepreneurship visions with Si Katara, a friend and UW computer science and engineering graduate with Silicon Valley experience in software architecture and project management.

“In early 2005 George and Si sat down with me and said the time was right to commercialize our body of expertise by establishing a company to develop a broader array of online training programs for the paving industry,” Mahoney said.

The team turned to Gail Dykstra, a C4C technology manager, for assistance in exploring goals and options and in developing a business plan. The four partners—Mahoney, Muench, White and Katara—founded Pavia Systems in September 2005 and, with Dykstra’s assistance, in 2006 secured a flexible agreement for licensing UW intellectual property that has enabled the company to prosper even in a challenging economic climate.

“Gail was phenomenal and brought many insights to the table,” White said. “She was critical in showing us the steps and urging us to form a company. Her encouragement gave us the confidence to take that leap on our own.”

Bridging Traditional Industry and High Technology

Mahoney suggested the company name Pavia (pronounced Pah-VEE-uh), which has roots in an ancient Roman outpost with a strategic roadway and bridge crossing the Ticino River.

“Pavia is a great name because we have created a unique space where we are a bridge to online technology for a very traditional industry,” White said. “By providing our customers the ability to train their workforce more efficiently than traditional methods, we can push the boundaries of how training is delivered and consumed within their organization.”

The National Asphalt Paving Association (NAPA), an industry trade group, partnered with Pavia to be its exclusive provider of online training. In collaboration with NAPA, Steve Muench developed a computer-based learning tool designed to teach managers, engineers, and technicians about a specific process called Superpave to design asphalt paving mixes and test them. With C4C assistance, UW retained the copyright to the online-training version, known as Virtual Superpave Lab. The latest collaboration with NAPA is a RoadReady Operator series Pavia offers to companies for online training of new employees on job safety, best practices, and compliance. All 10 hours of training fulfill NAPA’s Diamond Paving Commendation, which recognizes firms that adhere to best practices for product quality, safety, and training.

Reducing Tensions between Road Builders and Public Agencies

“The road building industry is traditionally a late adopter of new technologies that can help their operations run more efficiently,” Katara said. “Through consistency and transparency, Pavia can help reduce the inherent tensions between contractors that build or repair roadways and need to make a profit, and public agencies that own the roads, set design or repair specifications, and inspect the work to determine final payments.”

The problem is that public agencies and contractors have been using different approaches for training employees and testing to assess compliance with standards. Pavia recently completed a pilot project for CalTrans that put agency employees and contractor employees from the private sector through an online-training pilot for materials testing in California. Results from the post-course survey of participants rated the experience highly and expressed interest in further integration of online training in California.

“When both sides work from the same playbook, tensions between agencies and industry will decrease and the quality of the California highway system will go up,” Katara said.

Thriving Despite an Industry Downturn

The current economic climate is placing tremendous pressure on public agency and industry budgets. By adding an online training component to their workforce development strategies, organizations enjoy large cost savings and increased measurement and accountability benefits that become increasingly critical in lean times. This becomes especially important when that savings includes significant taxpayer dollars in reduced travel and training costs.

Pavia developed online training programs in English, French, Spanish, and Portuguese for US-based environmental unit of Lafarge, a Paris-based construction materials supplier with a presence in 78 countries more than 70,000 employees worldwide. Previously the company would fly trainers to worksites to get employees up to speed on new practices. With Pavia’s scalable system, the Lafarge can efficiently and more economically offer training to tens of thousands of workers anywhere at any time.

Pavia now has 120 clients and locally works with Washington State DOT and Lakeside Industries, headquartered in Issaquah and a highly respected leader in asphalt paving in the Northwest. Over the last three years, Pavia’s revenues have grown 53 percent — impressive given how hard the economic recession hit the construction sector. Katara and White plan to consult with C4C entrepreneurs in residence for advice on identifying and pursuing new market opportunities and on the best approaches for scaling up their business operations.

“We are poised to grow even more rapidly when the industry rebounds,” White said. “We have built a reputation as a thought leader and technology leader, and our major customers are already asking for online training products in other aspects of infrastructure construction.”

Read this article on the University of Washington’s Center for Commercialization website.

Empirical Design

Empirical design is based on previous experience with roadway structures. This experience can either be a result of previous roadway designs and their performance in the field, or testing. Tests for structural design are carried out on special test tracks, which are subjected to controlled loads. Pavement response is measured through observation and instrumentation. Empirical methods do not seek to determine the mechanisms behind loadings and roadway failure, but rather develop reliable models of how roadways perform. As a result, these methods are used in situations where there is a great deal of experience with projects in similar conditions. Empirical design methodology is very common in practice. Notable procedures which use this approach are the AASHO Road Test developed in the 1960′s, and the widely used 1993 AASHTO Design equation.

Mechanistic-Empirical Design

Mechanistic-Empirical Design, or M-E Design, attempts to use the theories of mechanics to more wholly understand roadway behavior. Mechanistic-Empirical models use mathematical models to emulate the relationships between loads, stresses, strains, deflections, and damage in a pavement structure. However, as the name infers, there is still an empirical component to these types of models. Experience with previous designs and testing are commonly used to determine the levels of stress and deflection which cause failure. In this way, M-E designs are still grounded in the past experiences of transportation agencies. M-E designs can be based on techniques such as a layered elastic model, which models each layer in the pavement as a homogenous material and computes reactions to loads throughout its depth. In addition, M-E designs can be based on computer based finite element models, which analyze pavements by breaking them up into a large number of distinct smaller elements. Groups such as the National Cooperative Highway Research Program have developed design procedures based on M-E design.

Looking back, the federal government has tried to estimate the cost of job creation through each strategy. Direct government investment has created jobs at an estimated price of $92,000 per job year. This includes employment that is direct, indirect, or induced. Tax cuts have created jobs at a rate of $145,000 each, and state relief has provided jobs at a rate of $117,000 each.

In 2007, the FHWA estimated that $1 billion of highway investment would create approximately 27,800 jobs. In comparison, investments in electricity generation and transmission yield around 14,500 jobs while investments in water infrastructure create about 19,800. Assuming that these jobs last at least one year, this comes out to about $36,000 per job for highway investment. This is based on four year old data, and an updated figure of the job output per dollar spent is almost certainly lower than the 2007 estimate. While the ARRA has other goals than raw job creation, these numbers indicate that investment in transportation is a competitive means of getting people back to work. As estimates are improved based on factors such as the current price of construction materials, close attention should be paid to which strategies are the most effective job-creators.

For additional information as well as sources from this edition of the RoadReady Newsletter and blog check out the following links:

Estimates of Job Creation from ARRA

Urban Mobility Report

The Economic Importance of the National Highway System

Employment Benefits of Highway Infrastructure Investment

Highways and the Economy

Freight Bottlenecks on the Highways

Investment and Job Creation

Understanding the Gas Tax

In addition to roadway safety, research has been done on the impacts of different weather conditions on traffic flow. A Federal Highway Administration publication looked at data from Baltimore, the Twin Cities, and Seattle to assess the effects of different weather types on traffic flow parameters. Interestingly, weather conditions were not found to impact the density for which traffic jams occur. However, the presence of light snow decreased traffic capacity by as much as twenty percent, and free flow speed by as much as sixteen percent. The study also noted that traffic usually moved slower in snowy conditions in the Twin Cities than in Baltimore, despite snow being more common in the former. One explanation for this result was that drivers were more aware of the dangers of driving in adverse conditions. Clearly, snow and ice have are a burden on our highways, and improved measures to combat their effects will benefit our transportation networks.

For more resources on driving and winter conditions, check out the following links:

Effects of Snowfalls on Motor Vehicle Collisions, Injuries, and Fatalities

Empirical Studies on Traffic Flow in Inclement Weather

A Synthesis on Studded Tires

A standard sieve nest used for gradation testing

Size and Gradation

One of the most well-known and common aggregate tests is the sieve test. Used for determining the gradation of an aggregate sample, the sieve test, aptly named, involves passing the aggregate through a number sieves. Each sieve consists of a metal cylinder with a wire screen at the bottom, which contain square holes of a specified width. Therefore, any rock that passes through a given sieve must have maximum dimensions smaller than the diagonal of the square. Sieves are stacked sequentially, with larger sized holes at the top, and smaller sizes at the bottom. The specific sieves to be used depend upon the particular specifications for the aggregate. Material is introduced to the top sieve, and the entire stack is agitated to promote passing of the particles through the screens. After a specified time interval, the mass of the aggregate retained on each of the sieves is weighed. This allows calculation of the proportion of the total sample within each size range.

Aggregate Shape

While gradation affects how dense an aggregate matrix is, the shape of the aggregate also impacts the strength of this matrix and how particles lock together. Depending on the size of aggregate, shape is assessed in different ways. For large aggregate particles, shape is determined by visual inspection. Depending on specifications, aggregate particles are divided into different categories based on the number of fractured faces. Generally, a number of required fractured faces is determined, and particles are designated as either pass or fail. The percentages of particles that pass and fail are determined on a by-mass basis.

Fine aggregate particles are too small and numerous for visual inspection, so a different method must be used. Because particle shape cannot be assessed directly, the void content of uncompacted aggregate is used to estimate this parameter. In general, the more angular an aggregate sample, the more resistant to compaction. Therefore, the presence of angular faces and rough particles will increase the void content of the aggregate. An uncompacted condition is achieved by passing the sample through a funnel and allowing it to fall into a cylinder of known volume. The mass of the aggregate in the sample is then measured, and air void percentage is calculated from the specific gravity of the aggregate.

A rotating drum for toughness testing

Durability and Toughness

The ability of aggregates to withstand freeze-thaw cycles (durability) can be extremely important in asphalt pavements depending on weather conditions. Aggregates can be damaged when trapped water freezes inside of individual particles and expands. Resistance to this phenomenon is gauged using soundness tests, which simulate the formulation of ice crystals through chemical processes. Aggregate samples are placed in a sulfate solution, which causes salt crystals to form in the aggregate pores. Like ice crystals, these crystals create outward pressure on the aggregates, and can lead to cracks and breaks. The aggregate sample is subjected to a number of repetitions of this process, and sieved to assess particle disintegration.

Aggregate toughness is determined through brute force. Aggregates are placed in a rotating drum, along with a number of steel balls. The drum is rotated at a specified speed and duration, allowing the steel balls to crush the aggregates inside to a certain extent. Again, this test is concluded by sieving the remaining material to determine the amount of crushing it has undergone. This test is commonly called the Los Angeles abrasion test.

For additional information on aggregate testing, check out the following links:

Gradation Test

Los Angeles Abrasion Test

Coarse Aggregate Angularity

Fine Aggregate Angularity

Aggregate Testing Bundle-Designed to familiarize technicians and engineers with the origins, procedures, calculations, and results associated with common aggregate tests, this bundle is comprehensive in its coverage in all things related to determining aggregate quality.

In the tables below, we’ve provided some temperature data for cities around the U.S. and across the globe. Each entry indicates the average daily high for that month in that city in degrees Fahrenheit. Cold weather paving can be broadly defined as paving when the air temperature is below 50 degrees Fahrenheit. Red numbers in the graph indicate months where the average daily high is above 60 degrees, and therefore paving can generally be safely conducted without worrying about cool paving measures. Green entries are those which fall between 50 and 60 degrees, indicating the range where temperature could become an issue depending on immediate conditions. Blue months are those where daily high falls below 50 degrees. In these ranges, cold paving measures will most likely be an important factor, if paving is conducted at all. Included is a map showing where in the U.S. the data is taken from. Note that because these are values of daily highs, any night paving will be in significantly colder temperatures than those shown.

Average daily high values by month in selected U.S. cities (degrees Fahrenheit)

Locations of U.S. temperature data

Average daily high values by month in selected international cities (degrees Fahrenheit)

For temperature data and additional cool paving resources, check out the following links:

National Climatic Data Center

Weatherbase.com

PaveCool (free pavement temperature software from MnDOT)

Temperature and Compaction Effects

In this week’s edition of the RoadReady Newsletter, we explored the history of roadway tolling as well as modern innovations. The amount of roadway tolling projects in the U.S. is growing significantly, but just how does the public feel about roadway tolling? While one might expect that the general public is opposed to paying to drive on their roads and bridges, research has shown that this isn’t the case. Let’s take a look at a few studies of public opinion on tolling conducted in the last few years.

In 2010, HNTB, a national infrastructure firm, conducted a nationwide opinion study on general tolling issues. They found that 84% of Americans support the consideration of tolling for individual projects, as well as for general funding. Over twice as many respondents supported funding of new roadways using toll revenues than those that supported an increase in the gas tax. 68% of respondents agreed that they would pay higher tolls if it saved them travel time, and of those that drive on tolled roads and bridges, 76% were satisfied with their current tolling systems.

The public is often willing to pay tolls in return for reduced congestion and travel time

In 2008, the Transportation Research Board (TRB) conducted a detailed survey of state experiences with tolling, and included feedback from around the world. Rather than directly surveying the public, the TRB compiled a large number of individual studies conducted by local agencies to create a broad picture of public opinion. The general conclusion of this study was that on the whole, the public is supportive of roadway tolling as a source of roadway funding. The sheer volume of data available also suggested that transportation agencies are very conscious of public opinion when planning tolling projects. Researchers also pointed out an interesting phenomenon in tolling policy. Often, politicians assume that tolling projects are unpopular with constituents, while the opposite is usually true. The study pointed to a particular survey which followed the governor of Illinois’ proposal to remove tolling from the Illinois Tollway. In fact, the survey showed that a majority of respondents supported tolling on the roadway for system maintenance and rehabilitation.

Because of the level of direct impact and interaction with users, public opinion is an important factor to consider on any tolling project. To date, transportation agencies have had a good track record of measuring this crucial variable prior to the decision making process, and public attitude towards tolling seems generally favorable. With the growth in tolling that is likely to occur in the coming years, this is an issue that should be watched closely.

For more information on public opinion, check out the following surveys:

HNTB – Americans Prefer Tolls Over Taxes

TRB – Compilation of Public Opinion Data on Tolls and Road Pricing

Public Opinion on Tolling

For general resources on roadway tolling:

AASHTO-Toll Funding

Current Toll Road Activity in the U.S.

Porous European Mix in Georgia

In 2009, the Georgia DOT decided to use micro-milling for the rehabilitation of a 15.6 mile stretch of I-75 near Macon, GA. In recent years, Georgia has been using a porous European mix (PEM) to overlay its interstate highways. However, concerns about poor bonding and water entrapment have prevented Georgia from placing this wearing course directly on traditionally milled surfaces. As a result, an overlay of stone matrix asphalt would typically be placed before the PEM. The improved smoothness provided by micro-milling and decreased ridge to valley depths presented Georgia with an opportunity to skip this step, saving significant amounts of time and money. By authoring special provisions for this unprecedented procedure and placing the PEM directly on the micro-milled surface, Georgia saved about $5.4 million, or $58,000 per lane mile.

To evaluate the effectiveness of the treatment, testing was conducted on cores of the finished surface. Tests were favorable regarding both moisture damage as well as rutting. When evaluating bond strength between the top layer and the micro-milled surface, the study determined that slippage risk was marginal in the short term, but that the bond was performing well after a period of seven months.

Micro-milling has shown money saving potential in Georgia

Performance Planing in Virginia

In 2004, Virginia conducted a series of pilot projects to evaluate their regulations for temporary lane drop-offs on temporary access highways. These drop-offs are created when a single lane is either milled or overlaid, and traffic is opened prior to leveling the adjacent surface. As part of these projects, VDOT also compared performance planing to typical mill-and-fill operations, as well as straight overlays without milling. Performance planing referred to creation of a smoother milled surface than traditional milling, and was accomplished by micro-milling in each case. The goal of the performance planing was to create a safer driving surface when the milled pavement was to be opened to traffic. In addition to comparing the milling treatments, this allowed VDOT to create a specification for performance planing.

The study, which included projects on two interstate highways, concluded that the micro-milling produced a smooth, uniform surface. In addition, the material left behind by micro-milling was more uniform, making it easier to collect from the roadway. Any remaining material was removed by traffic, leaving a clean roadway surface. The study noted that while bond strength on overlays has appeared to improve, the agency must wait to assess long-term performance.

To learn more about the projects above, as well milling basics, check out the links below:

Micro-milling in Georgia

Micro-milling in Virginia

Surface Preparation

On Board Sound Intensity

On board sound intensity (OBSI) is a common method for measuring pavement noise and consists of a pair of microphones mounted near the tire of a vehicle. Noise intensity, phase, and amplitude are measured as the vehicle drives across the pavement. This allows determination of the direction of noise, rather than just its magnitude, to more accurately characterize its impacts. Testing standards dictate a vehicle speed of 60 mph, and the specific type of tire to be used. In addition, the vehicle must in be in suitable condition and not make any extraneous noises.

Close Proximity Methods

Close proximity methods (CPX) use measurements taken with a device similar to the OBSI system, except the measurements of sound pressure, rather than sound intensity, are taken. Measurement of sound pressure rather than sound intensity is generally seen as a less sophisticated method, as it allows less understanding of directional characteristics, is more easily contaminated by outside noises, and is less correlated to noise at roadside.

Pass By Measurements

Passby (PB) measurements are taken using a microphone placed on the side of the roadway. These can either take statistically based samples of real traffic noise, or be used in conjuction with test vehicles. Like CPX, PB measure sound pressure rather than intensity. Unlike the vehicle mounted methods, passby measurements account for all aspects of vehicle noise, including pavement-tire contact, aerodynamic effects, engine and exhaust noise.
For additional information on pavement noise, check out the following links:

Quiet Pavement

Highway Traffic Noise-FHWA

Rubberized Asphalt in Arizona