State Highway Agencies Research Articles

Design of Rigid Pavements in Iowa Using the Mechanistic-Empirical Pavement Design Guide

The Iowa Dept of Transportation (DOT) currently utilizes the empirically-based American Association of State Highway and Transportation Officials (AASHTO) pavement design procedures originally derived from the 1960 Road Test data. It is clear that these empirical procedures are no longer applicable to current conditions in Iowa. With the release of the new Mechanistic-Empirical Pavement Design Guide (MEPDG) in the USA, there is a big shift in pavement analysis and design and many state highway agencies undertake initiatives to implement the MEPDG. In order to effectively and efficiently transition to the MEPDG and accelerate its adoption, the Iowa DOT needs a detailed implementation and training strategy. In support of the MEPDG implementation initiatives, sensitivity studies were conducted using the MEPDG software to identify design inputs pertaining to both rigid pavements and flexible pavements that are of particular sensitivity in Iowa. This paper is the first of the two companion papers discussing the need for implementing the MEPDG in Iowa, benefits of implementing the MEPDG in Iowa, and the results of rigid pavement input parameter sensitivity analysis. The results of flexible pavement design inputs sensitivity analysis and implementation recommendations are presented in the second paper.

A construction quality index for highway construction

Changes in policy regarding the use of contractor‐conducted testing in quality assurance decisions have hit state highway agencies (SHAs) during a time of continuing reduction in agency personnel. These changes have increased the need for quality‐driven contractors. This, coupled with more agencies adopting specifications tied to performance, places more requirements on contractors to emphasize quality management in their operations. There is a need for rational, comprehensive methods to evaluate a contractor's end product from a quality perspective; thus, there is a need for new techniques and approaches for examining and rating the quality of performance. Researchers and practitioners alike should benefit from this description of the construction quality index (CQI) developed through a grant from the Florida Department of Transportation. The CQI is a rating of the quality of materials and workmanship on highway projects that, unlike current quality rating models used by SHAs, is completely objective. Under limited validation testing, the model proved able to assign quality index values consistent with the owner's level of satisfaction with the overall project.

Simple Procedure to Assess Performance and Cost Benefits of Using Recycled Materials in Pavement Construction

The use of recycled materials in pavement engineering has a great potential to benefit our society in terms of reducing demands on natural pavement materials, reducing environmental problems, and conserving energy. However, pavement design/construction practitioners often hesitate to use recycled materials due to the lack of cost benefit and performance information. This paper presents a simple approach to evaluate economic effects of using recycled materials in pavement construction based on in situ pavement testing procedures. These testing procedures, including dynamic cone penetrometer, California bearing ratio, Dynaflect, and falling weight defelectometer, are commonly employed by state highway agencies. A full-scale accelerated pavement test section was built to investigate the performance of different base course materials: Louisiana Class II crushed limestone, foamed-asphalt-treated recycled asphalt concrete, fly-ash-stabilized blended calcium sulfate (BCS), and BCS stabilized with the 120 grade ground granulated blast furnace-slag (GGBFS). Among these base materials, GGBFS-stabilized BCS was found to have the highest strength and stiffness. On the basis of these field testing results, life-cycle cost analyses showed that the GGBFS-stabilized BCS provides a durable and cost-effective alternative to traditional pavement base materials.

Liquidated Damages: Review of Current State of the Practice

Liquidated damages (LDs) are contractually specified damages that provide restitution for additional owner costs incurred from contractor delayed completion. Established legal precedence requires owners to specify rates that are a good faith pre-estimate of actual anticipated damages. Additionally, the Federal Highway Administration provides guidance to state highway agencies (SHAs) in developing these rates. In reviewing current practices, SHAs were surveyed about individual LD practices utilized. Survey results are divided into three categories for discussion purposes: (1) contractual practices; (2) estimating practices; and (3) administrative practices. All SHAs chose to recover damages through a contractual LD clause although implementation varies. SHA estimating practices are generally not detailed and tend to place rates at the low end of actual damages. Few SHAs verify estimated rates with actual project cost experiences. Administrative practices have field personnel administering the primary eleme...

Long-Term Bridge Performance Program Begins

This article describes a five-year bridge study to be undertaken by the Center for Advanced Infrastructure and Transportation (CAIT), which is located at Rutgers University in New Jersey. The study is part of the Federal Highway Administration’s 20-year Long-Term Bridge Performance Program, which seeks to better understand how bridges perform under the various complex stresses they undergo throughout their lifetimes. The CAIT team will collect data on management practices, bridge deterioration, and the effectiveness of various maintenance practices on some 400 bridges less than 50 years old and not structurally deficient. From that 400, 20 will be chosen for several types of instrumentation that will monitor humidity levels, corrosion, and chemical changes as bridges deteriorate. In addition, the researchers will gather information from state highway departments and other agencies that maintain bridges.

Streamlined Strategies for Faster, Less Traffic-Disruptive Highway Rehabilitation in Urban Networks

The need for faster, less traffic-disruptive rehabilitation for aging highway infrastructure is an emerging concern for many state highway agencies. In response to this concern, the California Department of Transportation (Caltrans) launched the Long-Life Pavement Rehabilitation Strategies (LLPRS) program in 1998 to rebuild 2,800 lane kilometers of high-volume urban freeway with premium pavements that will last 30+ years and require minimal maintenance over their service life. This paper presents innovative strategies and technologies for achieving faster project completion with less traffic disruption as applied on three experimental LLPRS projects. The research team and the Caltrans project team used Construction Analysis for Pavement Rehabilitation Strategies (CA4PRS) software from the initial planning and design stages to implement the most economical rehabilitation strategies for the projects. The postconstruction analysis of all three LLPRS projects, made with data collected during construction, revealed a close match with the preconstruction schedule estimate generated by CA4PRS, validating the software's scheduling reliability. Incentive-disincentive contractual provisions proved effective for shortening project duration on all three LLPRS projects, which were time critical because of their heavy traffic volume. Resultant traffic data demonstrate the importance of a public outreach campaign that convinced motorists to use alternative routes or to adjust their commuting modes, resulting in significantly lower traffic demand in the construction work zone. The strategies and lessons addressed in this paper will help state highway agencies and contractors maximize construction productivity for early project completion and minimize inconvenience to the traveling public.

Sampling Schemes for Weigh-in-Motion Traffic Data Collection

Weigh-in-motion (WIM) technology has been widely used in highway traffic monitoring to support design and reconstruction of pavement structures. WIM systems are capable of continuously collecting vehicle size and weight data. However, collecting, storing, and processing the large amount of data required is costly. The cost is a critical concern of many state highway agencies (SHAs) because of their budget limitations and resource constraints. To address this issue, adopting sampled data instead of complete or population data has been recommended in most SHAs. However, it has been recognized that a gap inevitably exists between data samples and population. Therefore, a balance between data needs in pavement design and cost in data supply should be obtained. The effect of different sampling schemes on data accuracy on the basis of traffic information collected by WIM systems in Texas was comprehensively investigated. Three criteria involving both mathematical implication and engineering context were developed for evaluation of sampled data accuracy. A relationship between typical sampling schemes and data accuracy was established. The results and suggestions can provide more cost-effective and efficient WIM data collection for SHAs.

Highway Construction Quality Index for Florida

The Florida Department of Transportation (FDOT) is developing strategies to improve the quality of transportation infrastructure while coping with changes in business models and reductions in agency personnel. Nationwide, policy is changing more quickly than ever, and every policy change reinforces the need for contractors who perform high-quality work. There have been several initiatives in the past to develop some kind of rational, objective system of rating the quality of highway construction projects. There have also been initiatives to utilize these ratings for substantial issues such as contractor qualification and bidding purposes, but not one state uses their quality ratings for anything more substantial than setting contractors’ bidding ceilings. Some states do not use these ratings at all and some states do not even rate the quality of their projects. One of the chief complaints against current systems is their subjectivity. The construction quality index, developed through a grant from FDOT, is a rating of the quality of materials and workmanship on highway projects that, unlike current quality rating models used by state highway agencies, is totally objective. Under limited validation testing, the model assigned quality index values consistent with the owner's level of satisfaction with the project.

Effect of Traffic Load Measurement Bias on Pavement Life Prediction

The new Mechanistic-Empirical Pavement Design Guide (MEPDG) requires comprehensive traffic inputs to predict pavement performance. Axle load spectra play a critical role in the impact of traffic on pavement performance. Weigh-in-motion (WIM) systems are becoming widely used as an efficient means of collecting traffic load data for mechanistic pavement design. The quality of the WIM-based data, however, remains a concern among pavement engineers. Previous research showed that WIM equipment calibration bias may lead to significant bias in the estimation of equivalent single-axle loads. This study investigated the effect of traffic load measurement bias due to WIM measurement errors on pavement life prediction on the basis of the mechanistic-empirical approach proposed by MEPDG. The results of this study not only support but also advance the existing research in this critical area. The findings of this study can be used to estimate pavement life prediction bias when inaccurate WIM data are used. They can also serve as guidelines for state highway agencies for the selection of WIM equipment and the establishment of criteria for equipment calibration.

Robust Determination of Liquidated Damage Rates for State Highway Agencies

Liquidated damages (LDs) in highway construction contracts are daily monetary rates meant to compensate the owning agency for additional costs incurred because a project did not meet its completion date because of contractor delay. When LD provisions are challenged in court, provisions that lack proper documentation outlining the procedure used to determine rates have been deemed a penalty and unenforceable. This research effort sought to develop a methodology for developing a schedule of LD rates to be adopted by the Alabama Department of Transportation (ALDOT). The procedure outlined is to be used periodically to review and update the LD rates found in ALDOT's standard specifications for highway construction contracts, since their current schedule and review procedure has come under legal scrutiny. A statistically justifiable procedure was developed to calculate LD rates using historical project cost accounting data to create a traditional provision based on FHWA guidelines with the LD rates stipulated in a contract-size categorized table. The proposed procedure was then compared with a typical procedure used for developing LD rates. After comparisons, the proposed procedure stipulating LD rates in a table by contract value was determined to be the more robust method. The final product of this research is stepwise guidelines for practitioners to use on a periodic basis to review and update their schedule of LD rates.

Relating Axle Load Spectra to Truck Gross Vehicle Weights and Volumes

Axle load spectra have been used to develop the mechanistic-empirical pavement design guide (M-E PDG). Use of these load spectra provides a more direct and rational approach for the analysis and design of pavement structures to estimate the effects of actual traffic on pavement response and distress. However, the demand for specific truck- and axle load-related data makes the collection of axle load spectra a very complicated, costly, and labor-intensive operation. Due to limited resources available in state and local highway agencies for traffic data collection, the M-E PDG allows for various levels of traffic data collection and analysis. These levels vary from site-specific (Level 1) to regional average (Level 3) traffic load and volume data. This paper explores the possibility of extracting axle loads from truck weight and volume data and presents a practical method of modeling axle load spectra. Axle load-related data used in the analyses cover diversified geographical locations in the United States. The results show that truck weights and proportions on a highway can be used to estimate individual axle load spectra for various axle configurations. The practical implication of these results is that truck weights, which can be measured easily or estimated from existing data, can be related to the axle loads if accurate and rational models are developed for a region based on the local truck traffic characteristics and weights. Such estimates will be superior to assuming a Level 3 input for axle load spectra in the new M-E PDG.

Methodology of Assessing Testing Variation for Volumetric Quantities in Hot Mix Asphalt Production

Abstract Increasingly, in road construction, pay incentives and disincentives are being related to both the average test results that are obtained during quality assurance testing as well as the variability associated with these values. As a result, state highway agencies must be fully aware of the expected variability that can be associated with each acceptance test since the results will not only be used for acceptance but may be used for pay adjustment also. In this study, a methodology was developed to assess the testing variability in hot-mix asphalt production. The study focused on determining allowable testing variations for the calculated volumetric quantities, including the air voids content and voids in mineral aggregate (VMA) determined from gyratory compacted specimens. A new standard of determining an allowable testing variation for VMA was developed. Furthermore, a test data analysis plan to extract the testing variation from the total measured variation for the hot-mix asphalt quality parameters was developed.

Evaluation of Current State of Flexible Overlay Design for Rigid and Composite Pavements in the United States

Current composite pavement practices and key hot-mix asphalt (HMA) overlay design features, mainly to mitigate reflective cracking in the HMA overlay, used by state highway agencies in the United States are summarized. This information was obtained from a comprehensive survey conducted from January to May 2006 under a research effort for the New Jersey Department of Transportation to help minimize or retard the onset of reflective cracking in HMA overlays on portland cement concrete (PCC)/composite pavements. Information is provided on reflective cracking mitigation methods (successes and failures), current in-place composite/PCC pavement designs, treatments to prepare PCC pavement before HMA overlay and typical time until reflective cracking appears in the HMA overlay. Parameters that state agencies use to characterize pavement site conditions, including nondestructive testing, traffic conditions, and laboratory testing are also given. Further analysis is conducted by comparing the low temperature climatic conditions of the state to the low temperature performance grade of the asphalt binder commonly used in the HMA overlay. This examination and summary of survey findings on current pavement design practices and design features on the use of flexible overlays for rigid pavements in the United States will be of interest to state agencies, practitioners, and pavement researchers.

Rapid Alternative for Laboratory Determination of Resilient Modulus Input Values on Stabilized Materials for AASHTO Mechanistic-Empirical Design Guide

NCHRP is in the final stages of developing and implementing a new mechanistic-empirical pavement design guide (MEPDG) to be used by all state highway agencies for layer thickness design. Once adopted, it will become the national procedure required on all federally aided projects. A key material property to be used in the design will be the resilient modulus value, which either can be obtained from laboratory testing or can be backcalculated from deflection data collected with falling weight deflectometers. It is important that realistic design moduli values be used. The standard test method for resilient modulus of subgrade soils and untreated base and subbase materials is AASHTO T307-99. However, the setup for this procedure is both difficult and time-consuming, and the equipment required to run this test is expensive. With the low strain levels used, it is likely that accurate instrumentation will be problematic for most state departments of transportation. The free-free resonant column test is a simple, nondestructive laboratory test method for determining the seismic modulus of pavement materials; it takes approximately 5 min to setup and complete. The equipment costs less than $4,000. For the tests conducted, it appears that the seismic modulus device is a better and more repeatable test for estimating the resilient modulus of stabilized materials, and it shows great potential for acquiring reasonable resilient modulus input values for the new AASHTO MEPDG.

Genetic Algorithms–Based Network Optimization System with Multiple Objectives

In any engineering decision-making process, it is a common problem to formulate a model with multiple objectives and to obtain proper answers. If the objectives are opposing, the problem then becomes finding the best possible design that identifies the best compromise between the opposing objectives. In a pavement management system of a state highway agency, engineers constantly struggle with performance requirements and limited budget. This situation results in an optimization problem with two conflicting objectives. The underlying algorithm of the classic network optimization system was coupled with genetic algorithm (GA) techniques to minimize budget and maximize performance of highway pavement networks in rehabilitation planning. GA is generally considered a powerful methodology in solving multiobjective problems. The data analysis demonstrated that the GA technique is applicable in producing workable solutions to a multiobjective pavement management problem.

FUNCTIONAL MODEL OF COST AND TIME FOR HIGHWAY CONSTRUCTION PROJECTS

It is commonly accepted that construction cost, time and quality performance has been regarded as the major success factors for a construction project. With the increasing use of innovative contracts in highway construction, the relationship between construction cost and time has become more crucial than ever. Improved control of time value has become necessary, for quantifying the functional relationship between construction cost and time. This study explores the functional relationship between highway construction cost and time. Data from projects of the Florida Department of Transportation (FDOT) in the US is utilized to develop and illustrate the quantifying model. The proposed model provides State Highway Agencies (SHAs) and contractors with increased control and understanding regarding the time value of highway construction projects.

Best Practices of Bridge System Management—A Synthesis

The paper’s primary purpose is to evaluate current practices in bridge management and inspection procedures in the United States and how State Highway Agencies (SHAs) follow U.S. Department of Transportation guidelines. The efficiency of SHA in utilizing the bridge management systems (BMSs) available to them is analyzed, and the agencies’ readiness to respond to events such as hurricanes, flooding, or earthquakes is evaluated. The paper addresses issues regarding bridges with unknown foundations, interviewing four structural engineers from three SHA regarding these topics. Bridge management officials across the country will benefit from this research by evaluating their agencies’ current practices in comparison with other state agencies. Findings show that state officials attempt to follow very closely the guidelines set by the federal government for bridge inspection and maintenance. However, it was also discovered that, during catastrophic events, agencies rely heavily on managing engineers’ experience ...

Effect of Coarse Aggregate Morphology on Permanent Deformation Behavior of Hot Mix Asphalt

This paper defined a complete set of imaging based indices for different levels of coarse aggregate morphologies, i.e., the flat and elongated (FE) ratio, angularity index (AI), and surface texture (ST) index, and investigated their effects on permanent deformation behavior of hot mix asphalt (HMA). Image analyzed coarse aggregates were used to prepare eighteen Superpave HMA specimens using job mix formulas from ten State highway agencies and tested for permanent deformation at a specified high temperature. The permanent deformation data when linked to the morphological indices of the coarse aggregate, showed the best correlations with the ST index. The FE ratio demonstrated no measurable effects on the permanent deformation due to low percentage of flat and elongated particles used in the mixes. The influences of the AI and ST indices on the permanent deformation were especially significant when differences in the asphalt mix aggregate gradations were properly considered. A possible mechanism of coarse aggregate morphology affecting the stability and permanent deformation behavior of HMA was proposed in terms of particle geometrical interference in HMA.

Legal Challenge to a Best-Value Procurement System

The U.S. highway industry has witnessed increased use of design/build project delivery and best-value procurement in the last decade. The industry is experiencing the growing pains of venturing into territory that was previously left to other sectors of design and construction. Inexperience with the system and the processes behind these systems by all parties, state highway agencies, designers, and contractors has occasionally led to protest filed with the court system. The precedents set by the decisions of the court will have a lasting effect on the industry as the exploration of delivery and procurement systems continue. One state highway agency that utilized a two-step best-value procurement process received a protest from one of the firms that was not successful in passing the qualifications phase of the procurement. The court found evidence to uphold the decision of the state highway agency through the transparent and documented evaluation process established by the state highway agency. Continued e...

Long-Term Effects of Magnesium Chloride and Other Concentrated Salt Solutions on Pavement and Structural Portland Cement Concrete

Many state highway agencies use various chemicals to deice or anti-ice pavement and bridge surfaces. Most often these are aqueous solutions of various chlorides (e.g., magnesium chloride, sodium chloride, and calcium chloride) or other chemicals such as calcium magnesium acetate, urea, or others. Possible detrimental effects to concrete caused by these chemicals have not been fully examined and documented. Mortar specimens of three different water-to-cement ratios (0.4, 0.5, and 0.6) were immersed in concentrated solutions of various chemical deicers and held above freezing at a constant temperature of 40°F up to 84 days. Considerable expansion and cracking were noted in specimens immersed in the MgCl2 and CaCl2 solutions. Petrographic analysis and quantitative microanalysis were used to positively identify the presence of Mg(OH)2 (brucite) formation in the outer layers of the specimens. Furthermore, the results presented clear evidence of calcium oxychloride formation in the specimens analyzed. Further research is being conducted, including the same immersion test at 40°F on portland cement concrete specimens, to identify whether this distress mechanism is of concern for structures such as roads and bridges when subjected to deicing chemicals containing CaCl2 or MgCl2.