Alternate Pavement Bidding (APB) is a process in which both concrete and asphalt pavement designs are developed for a project and the contractor selects which material to submit with his bid. The bid and pavement type that wins is the one that has the lowest life cycle costs. The goal of APB is to increase competition and lower cost by bringing additional contractors and pavement options to the bidding table. In 2010, the North Carolina Department of Transportation (NCDOT) and the North Carolina Turnpike Authority (NCTA) started exploring the use of the APB. As part of development process, NCTA/NCDOT asked representatives from both the concrete and asphalt paving industries to participate. In reviewing the APB and LCCA models used by other Agencies, the concrete industry identified several reoccurring engineering and economic factors that they believed were correlated with successful implementation of an APB model. This paper presents the information given to the NCDOT / NCTA by the concrete paving industry in order to have a more comprehensive process that accurately reflects the risk, costs, and performance of the competing alternatives.

In 1991 an experimental project was built on a Louisville, Kentucky landfill access road. The purpose was to evaluate the feasibility of concrete whitetopping overlays less than 4 inches thick for residential streets, parking and other low-volume applications. The landfill site provided accelerated loading conditions and weight-monitored truck traffic data. Two sections with different thicknesses were built, one 2 inches and the other 3.5 inches. The experiment also employed unconventional 6 foot and 2 foot joint patterns. These constituted the major variables of the test project. The landfill traffic conditions necessitated "Fast Track" construction of the thin overlay experiment. The access road was only closed over one weekend and provided just a 4L5 hour window to complete the construction work. This paper includes a description of the ultra-thin overlay performance. As of September 1992, both sections on the project are performing well and have carried over 585,000 Equivalent Single Axle Loads (ESAL's). The designs have out-lived predictions by conventional pavement theory and models. The authors will discuss the influence of the joint spacing and the overlay bonding on the bending stress conditions within the overlay slabs. This paper will also document the design and construction of this project. The cooperation of all parties involved was a major factor and an outstanding tool for innovation. The ultra-thin concrete whitetopping concept could induce major changes to the construction and resurfacing of asphalt roads, streets and parking areas throughout the United States. The promise shown by this initial experiment warrants further experimentation and discussion.

This article presents a comprehensive study aimed at developing a mechanistic design procedure for Ultra-Thin Whitetopping (UTW) pavements, addressing a gap in existing pavement design methodologies for this innovative resurfacing technique. UTW involves the application of very thin concrete overlays on deteriorated asphalt pavements to create a bonded composite pavement system, leveraging high-quality concrete with close joint spacings and the inherent bond between concrete and asphalt to reduce overlay thickness. The research, sponsored by the Portland Cement Association and the American Concrete Pavement Association, combined literature reviews, field surveys, load testing, and both 3D and 2D finite element modeling to propose a design procedure that incorporates critical factors such as interface bonding, joint spacing, and the performance of concrete and asphalt under traffic loading and environmental stresses. The proposed design method, which is iterative in nature, aims to ensure the structural integrity and durability of UTW pavements by considering both concrete and asphalt fatigue, thereby providing a scientifically backed approach to determining optimal concrete thickness and joint spacing. This work is expected to enhance the performance and reliability of UTW pavements, encouraging their broader adoption in pavement rehabilitation projects. (Abstract generated by AI tool ChatGPT 4)

This study, led by Chung-Lung Wu, James W. Mack, Paul A. Okamoto, and Robert G. Packard, advances the understanding of faulting in concrete pavements by refining the erosion criteria introduced by the Portland Cement Association in 1984. Recognizing that heavy-axle loads contribute to slab corner and edge deflections, leading to pumping, erosion, and ultimately faulting of pavement joints, the research aimed to update these criteria with performance data available post-1984, considering various climatic and drainage conditions. The methodology encompassed incorporating mechanistic-based erosion criteria into thickness design procedures, focusing on slab deflections caused by heavy-axle loads. Using a refined erosion prediction model, the study correlated deflection criteria to AASHO Road Test performance data, adjusting for different slab thicknesses and support values. The model successfully predicts faulting by considering the rate of work done on the pavement, factoring in slab-foundation interface pressure, slab corner deflection, and the radius of relative stiffness. The results showed that environmental factors such as annual precipitation and joint spacing significantly impact joint faulting, with the use of edge drains being crucial for undoweled pavements. The research highlights the importance of considering local conditions in pavement design, demonstrating that adjustments to the PCA erosion criteria can effectively account for the effects of shoulders, aggregate interlock, and the use of dowel bars. This contribution is vital for developing more accurate and locally adaptable design guidelines for concrete pavements, ensuring their long-term performance and sustainability. (Abstract generated by AI tool ChatGPT 4)

With the passing of the Bipartisan Infrastructure Law in 2021, the US is poised to spend billions of dollars on its highways and roadways. Despite this enormous outlay of funds, the US highway infrastructure needs are still at an all-time high. There is about a $435 billion backlog of highway road repair projects, and over 40% of US roadways are in a poor/deficient condition, which is costing the country an additional $130 billion in extra vehicle repairs and operating costs, or over $1,000 per motorist per year. Improvement of the system is needed. The primary approach to address this challenge has typically been to increase funding. While more funding helps, agencies also need to be more efficient within their constrained budgets to get more out of their roadway and pavement investments. This paper will show how competition across paving industries can be used to lower pavement unit costs.

Future climate conditions are not going to resemble the past. Temperatures will be hotter, and storms will be stronger. However, pavements are still being designed assuming that past conditions will resemble the future. This is a bad assumption. When climate change and pavement resilience are discussed, the focus is often on the immediate impacts of the natural disaster. While this is important, pavement damage also occurs after the natural disaster when rescue, emergency response, recovery, and rebuilding activities are taking place, and the pavement, often in a weakened state, is subjected to increased volume of heavier traffic. This paper will show how current resiliency concepts and framework can be applied to pavements and how two cement-based solutions (concrete overlays and full depth reclamation with cement) can be used to improve pavement resilience and mitigate damage both during and after a natural disaster, using flooding as an example.

In 2009, the US cement and concrete industries established the Concrete Sustainability Hub at the Massachusetts Institute of Technology. A primary thrust of MIT's activities has been improving the Life Cycle Assessment practices to better quantify the environmental impacts over the life of a pavement. In their research, the MIT CSHub determined that the "use phase," and specifically Pavement Vehicle Interaction (PVI) has a very large impact on a Pavement's sustainability aspects. This paper will summarize the CSHub PVI research findings to date.

In 2009, the United States cement and concrete industries established the Concrete Sustainability Hub at the Massachusetts Institute of Technology to develop more sustainable and durable pavement infrastructure and buildings. With respect to pavements, two areas of focus have been on how the economic practices used in the pavement type selection process can be improved and how inter-industry competition (competition between industries) can lower agency pavement costs. With regard to the economic practices, MIT has focused on how the life cycle cost analysis (LCCA) process can be improved so that the results are more representative of the agency’s cost. With regard to competition, MIT has shown that sustained and viable competition between paving industries can lower bid prices. The goal of this paper is to summarize the relevant MIT CSHub pavement economic and competition research to date.

In 2009, the U. S. cement and concrete industries established the Concrete Sustainability Hub at the Massachusetts Institute of Technology. A primary thrust of MIT's activities has been improving the life cycle assessment practices to better quantify the environmental impacts over the life of a pavement. In their research, the MIT CSHub determined that the "use phase" can dominate the materials, construction, and maintenance phases of a pavement LCA and that two of the important factors in the use phase are pavement vehicle interaction (PVI) and Albedo. PVI describes the excess fuel emissions/energy from vehicles due to excess rolling resistance between the pavement and the vehicle. Albedo is the fraction of solar energy reflected by the Earth's surface, with lighter color, higher albedo surfaces reflecting more energy than lower albedo, darker surfaces. This paper will summarize the CSHub use phase research findings to date.

In 2009, the US cement and concrete industries established the Concrete Sustainability Hub at the Massachusetts Institute of Technology (MIT) in order to develop more sustainable and durable pavement infrastructure and buildings. With regards to pavements, a primary thrust of MIT's activities has been improving the Life Cycle Assessment practices to better quantify the environmental impacts over the life of a pavement. In doing their research, MIT determined that the environmental impact from the "use phase" almost always plays a substantial role and can often surpass the materials, construction and maintenance phases combined. Furthermore, they found that most of a pavement's use-phase impacts come from emissions by vehicles using the pavement due to excess rolling resistance between the pavement and the vehicle. The study of assessing how much excess fuel or energy is used by vehicles due to pavement affects is called pavement-vehicle interaction or PVI. This paper summarizes the PVI research findings to date and shows how incorporating PVI-related impacts into the decision-making process can lead to meaningful reductions in vehicle emissions.

For the design of new jointed plain concrete pavements (JPCPs), three national calibrations of the AASHTOWare Pavement ME have been necessary due to updates in either the prediction models or the calibration database. Local calibration is recommended to further refine predictions so that they better match a state’s experience. To date, local calibration efforts resulted in eight states changing one or more coefficients to a local value, while eleven states have decided to directly adopt national calibration coefficients. To determine the impact of local calibrations relative to the national calibration, a review of the national and local calibration efforts was completed. Local and national calibration coefficients were compared in two scenarios. In the first scenario, Pavement ME was employed to evaluate the performance of a hypothetical JPCP section. In the second scenario, Pavement ME was used as a tool for determining the thickness of pavements with various design features. It was found that for most states the pavement performance differed quite significantly between the local and national calibrations. However, in terms of design thickness, no evident difference could be statistically concluded for most of the states. In comparing designs developed using AASHTO 1993 Guide for Design of Pavement Structures, it was found that the Pavement ME yielded thinner designs regardless of the calibration coefficients used.

This research presents a study of visits to farmers' markets, a rapidly growing urban phenomenon in the U.S., from a geographic perspective. Although the social and economic impacts of farmers' markets have received considerable attention recently, examining farmers' market access in space-time is still lacking in the existing analytical frameworks. This study challenges conventional food access measures that have been primarily focused on the spatial separation between markets and consumers' homes and proposes a more realistic space-time based strategy. A survey was conducted on twelve markets in Tucson, Arizona. Analysis results show that majority of market patrons went to a market that was different from the one nearest to their homes, and the market choice, including the geographic location and the associated market operating time, was highly affected by patrons' other daily activities. The particular types of activities combined with farmers' market trips were found to vary temporally and fluctuate based on patron's employment characteristics. Our study suggests that conventional food access measures should be used in caution to assess farmers' market access as these measures can lead to an overestimate of the travel consumers are willing or even able to incur.

Contained in the Moving Ahead for Progress in the 21st Century (MAP-21) Transportation Legislation are three primary provisions that create a comprehensive, outcome-based program for pavements. The objective of this program is for States to invest resources in projects that will collectively make progress toward achievement of national goals. The principle provision – §150 National Goals and Performance Management Measures – requires that the United States Department of Transportation (USDOT) to develop performance measures and targets related to seven national goals, including maintaining the highway infrastructure assets in a state of good repair. The second provision – §119 National Highway Performance Program – requires the States to develop a risk-based asset management plan to improve or preserve the condition of assets through a program of projects that make progress toward achievement of the State targets for asset condition and performance of the system. The third provision – §135 Statewide and Nonmetropolitan Transportation planning – requires States to use a performance-based approach to transportation decision-making in their statewide transportation planning process to support the national goals. This paper shows how States can address these three provisions for pavements by using a concept called Remaining Service Life or RSL. RSL is a measurement of the time until the next rehabilitation of a pavement section. It is useful as a Performance Measure because it enhances pavement condition data by including pavement deterioration information. It is useful as part of an Asset Management Plan because it ensures investments are made to improve the life and usefulness of the highway system and it is useful as part of an Effective Planning Process because it gives agencies the long term information they need, with reasonable accuracy, to plan future maintenance and rehabilitation needs cost effectively.

Historically pavement designs have been based on an engineering analysis where the pavement thickness and features are chosen to meet the traffic, environmental, and subgrade conditions for the project. For concrete pavements, this means that the pavement is typically designed to last the entire design period (e.g., 20 to 40 years) without intermittent rehabilitation activities. Asphalt pavements, however, are designed with planned periodic future rehabilitation activities in mind. This often results in concrete pavements being overdesigned with high initial costs, but lower rehabilitation costs. Conversely asphalt pavements have lower initial costs, but higher rehabilitation costs. Though life cycle cost can influence the pavement type selection, more often the final pavement selection is based on initial costs. This paper presents a model to optimize concrete pavement designs by balancing the initial costs of the pavement, which is primarily affected by the thickness and specific design features used, and the rehabilitation costs of the pavement based on the pavement's predicted performance using the recently adopted American Association of Highway and Transportation Officials (AASHTO) Mechanistic Empirical Pavement Design Guide (MEPDG) and its companion software, DARWin-ME.

Life-cycle cost analysis (LCCA) is an economic procedure used to compare competing pavement designs over a defined analysis period, considering all significant costs expressed in equivalent present value dollars. A primary input into an LCCA is the discount rate, which accounts for the time value of money and converts future spending into present values. This method makes the future rehabilitation costs equivalent to current dollars and is essential in comparing the cost of alternative pavement designs. All state highway agencies that use LCCA in pavement type selection use a real discount rate, which removes the inflation portion in the present value calculation. The primary reason to use a real discount is that the analyst can use constant (today's) dollars in the analysis for the future rehabilitation costs. However, the implicit assumption in using a real discount rate is that inflation for all materials matches the general rate of inflation. This study shows that this assumption is not valid and that the inflation rates for asphalt and concrete (the two primary pavement materials) are different. Finally, the paper presents a procedure that highway agencies can use to account for differences in material-specific inflation rates. This procedure escalates today's constant dollar by the difference between each material's expected inflation rate and the general inflation rate and then discounts the escalated cost back by using the real discount rate.

The recent drive among consumers to purchase fresh, healthy and environmentally friendly food has brought about a renewed interest in farmers’ markets. However, ensuring the success of a farmers’ market is not an easy task. Unlike general grocery stores, farmers’ markets often have very limited hours of service and are distributed sparsely in space. Both spatial and temporal constraints that people experience in their daily lives limit their accessibility to a farmers’ market. This research incorporates such constraints in the service provision planning of farmers’ markets. In particular, two models are proposed to select locations and the associated service schedules for a fixed number of farmers’ markets. A case study is conducted in Tucson, Arizona to demonstrate the merits of the new approach.

Maximizing accessibility is often an important consideration in the location of a facility. This paper describes the development of a planning procedure based on a geographic information system (GIS) to assist decision makers in site selection when various accessibility criteria are considered. The procedure is illustrated in the context of siting a new women's and children's community center in Tucson, Arizona. First, suitable sites are identified as candidates on the basis of constraints related to transportation, land use, zoning, and so forth. Then a GIS-based decision support system is designed to assess the optimality of the candidate sites on the basis of accessibility by different population groups modeled, with the use of a multiobjective mathematical programming approach. Although this analysis focuses on a single facility, the methodology discussed, including the use of visual assessment tools and the development of the optimization model, can be used for multiple site selection and easily extended to other applications in which accessibility is a key component.