bluuebunny/crossref_metadata_2025 huggingface dataset:
Genetic Variants Associated With Glycine Metabolism and Their Role in Insulin Sensitivity and Type 2 Diabetes
Authors: Xie Weijia , Wood Andrew R. , Lyssenko Valeriya , Weedon Michael N. , Knowles Joshua W. , Alkayyali Sami , Assimes Themistocles L. , Quertermous Thomas , Abbasi Fahim , Paananen Jussi , Häring Hans , Hansen Torben , Pedersen Oluf , Smith Ulf , Laakso Markku ,   the MAGIC Investigators,   the DIAGRAM Consortium,   the GENESIS Consortium,   the RISC Consortium, Dekker Jacqueline M. , Nolan John J. , Groop Leif , Ferrannini Ele , Adam Klaus-Peter , Gall Walter E. , Frayling Timothy M. , Walker Mark
Published: February 2013

Circulating metabolites associated with insulin sensitivity may represent useful biomarkers, but their causal role in insulin sensitivity and diabetes is less certain. We previously identified novel metabolites correlated with insulin sensitivity measured by the hyperinsulinemic-euglycemic clamp. The top-ranking metabolites were in the glutathione and glycine biosynthesis pathways. We aimed to identify common genetic variants associated with metabolites in these pathways and test their role in insulin sensitivity and type 2 diabetes. With 1,004 nondiabetic individuals from the RISC study, we performed a genome-wide association study (GWAS) of 14 insulin sensitivity–related metabolites and one metabolite ratio. We replicated our results in the Botnia study (n = 342). We assessed the association of these variants with diabetes-related traits in GWAS meta-analyses (GENESIS [including RISC, EUGENE2, and Stanford], MAGIC, and DIAGRAM). We identified four associations with three metabolites—glycine (rs715 at CPS1), serine (rs478093 at PHGDH), and betaine (rs499368 at SLC6A12; rs17823642 at BHMT)—and one association signal with glycine-to-serine ratio (rs1107366 at ALDH1L1). There was no robust evidence for association between these variants and insulin resistance or diabetes. Genetic variants associated with genes in the glycine biosynthesis pathways do not provide consistent evidence for a role of glycine in diabetes-related traits.
Reevaluation of Fatty Acid Receptor 1 as a Drug Target for the Stimulation of Insulin Secretion in Humans
Authors: Wagner Robert , Kaiser Gabriele , Gerst Felicia , Christiansen Elisabeth , Due-Hansen Maria E. , Grundmann Manuel , Machicao Fausto , Peter Andreas , Kostenis Evi , Ulven Trond , Fritsche Andreas , Häring Hans-Ulrich , Ullrich Susanne
Published: February 2013

The role of free fatty acid receptor 1 (FFAR1/GPR40) in glucose homeostasis is still incompletely understood. Small receptor agonists stimulating insulin secretion are undergoing investigation for the treatment of type 2 diabetes. Surprisingly, genome-wide association studies did not discover diabetes risk variants in FFAR1. We reevaluated the role of FFAR1 in insulin secretion using a specific agonist, FFAR1-knockout mice and human islets. Nondiabetic individuals were metabolically phenotyped and genotyped. In vitro experiments indicated that palmitate and a specific FFAR1 agonist, TUG-469, stimulate glucose-induced insulin secretion through FFAR1. The proapoptotic effect of chronic exposure of β-cells to palmitate was independent of FFAR1. TUG-469 was protective, whereas inhibition of FFAR1 promoted apoptosis. In accordance with the proapoptotic effect of palmitate, in vivo cross-sectional observations demonstrated a negative association between fasting free fatty acids (NEFAs) and insulin secretion. Because NEFAs stimulate secretion through FFAR1, we examined the interaction of genetic variation in FFAR1 with NEFA and insulin secretion. The inverse association of NEFA and secretion was modulated by rs1573611 and became steeper for carriers of the minor allele. In conclusion, FFAR1 agonists support β-cell function, but variation in FFAR1 influences NEFA effects on insulin secretion and therefore could affect therapeutic efficacy of FFAR1 agonists.
Proinflammatory Cytokines, Adiponectin, and Increased Risk of Primary Cardiovascular Events in Diabetic Patients With or Without Renal Dysfunction
Authors: Schöttker Ben , Herder Christian , Rothenbacher Dietrich , Roden Michael , Kolb Hubert , Müller Heiko , Brenner Hermann
Published: February 2013

OBJECTIVE

Inflammatory processes contribute to both diabetes and cardiovascular risk. We wanted to investigate whether circulating concentrations of proinflammatory immune mediators and adiponectin in diabetic patients are associated with incident cardiovascular events.

RESEARCH DESIGN AND METHODS

In 1,038 participants with diabetes of the population-based ESTHER study, of whom 326 showed signs of renal dysfunction, Cox proportional hazards models were used to estimate hazard ratios (HRs) and 95% CIs for the association of increasing concentrations of C-reactive protein (CRP), interleukin-6 (IL-6), IL-18, macrophage migration inhibitory factor (MIF), adiponectin, and leptin with cardiovascular events (myocardial infarction, stroke, or fatal cardiovascular event) during a follow-up period of 8 years.

RESULTS

During follow-up, 161 subjects with diabetes experienced a primary cardiovascular event. Proinflammatory markers were not associated with a higher risk for primary cardiovascular events in the total study population after adjustment for multiple confounders. However, IL-6 and MIF were associated with cardiovascular events in subjects with renal dysfunction (HR for the comparison of top vs. bottom tertile 1.98 [95% CI 1.12–3.52], P [trend] = 0.10 for IL-6; 1.48 [0.87–2.51], P [trend] = 0.04 for MIF). Adiponectin levels were associated with cardiovascular events in the total population (1.48 [1.01–2.21], P [trend] = 0.03), and the association was even more pronounced in the subgroup with renal dysfunction (1.97 [1.08–3.57], P [trend] = 0.02).

CONCLUSIONS

In particular, the absence of an association between CRP and a U-shaped association of adiponectin levels with incident cardiovascular events show that associations between circulating immune mediators and cardiovascular risk differ between diabetic patients and subjects of the general population.
Glycation Gap Is Associated With Macroproteinuria but Not With Other Complications in Patients With Type 2 Diabetes
Authors: Cosson Emmanuel , Banu Isabela , Cussac-Pillegand Camille , Chen Qinda , Chiheb Sabrina , Jaber Yahya , Nguyen Minh Tuan , Charnaux Nathalie , Valensi Paul
Published: February 2013

OBJECTIVE

We investigated whether glycation gap (G-Gap), an index of intracellular glycation of proteins, was associated with diabetes complications.

RESEARCH DESIGN AND METHODS

We measured concomitantly HbA1c and fructosamine in 925 patients with type 2 diabetes to calculate the G-Gap, defined as the difference between measured HbA1c, and fructosamine-based predicted HbA1c. Patients were explored for retinopathy, nephropathy, peripheral neuropathy, cardiac autonomic neuropathy (n = 512), and silent myocardial ischemia (n = 506).

RESULTS

Macroproteinuria was the only complication that was associated with G-Gap (prevalence in the first, second, and third tertile of G-Gap: 2.9, 6.2, and 11.0%, respectively; P < 0.001). The G-Gap was higher in patients with macroproteinuria than in those without (1.06 ± 1.62 vs. 0.03 ± 1.30%; P < 0.0001). Because HbA1c was associated with both G-Gap (HbA1c 7.0 ± 1.4, 7.9 ± 1.4, and 10.1 ± 1.8% in the first, second, and third G-Gap tertile, respectively; P < 0.0001) and macroproteinuria (HbA1c 8.8 ± 2.2% if macroproteinuria, 8.3 ± 2.0% if none; P < 0.05), and because it could have been a confounder, we matched 54 patients with macroproteinuria and 200 patients without for HbA1c. Because macroproteinuria was associated with lower serum albumin and fructosamine levels, which might account for higher G-Gap, we calculated in this subpopulation albumin-indexed fructosamine and G-Gap; macroproteinuria was independently associated with male sex (odds ratio [OR] 3.2 [95% CI 1.5–6.7]; P < 0.01), hypertension (2.9 [1.1–7.5]; P < 0.05), and the third tertile of albumin-indexed G-Gap (2.3 [1.1–4.4]; P < 0.05) in multivariate analysis.

CONCLUSIONS

In type 2 diabetic patients, G-Gap was associated with macroproteinuria, independently of HbA1c, albumin levels, and confounding factors, suggesting a specific role of intracellular glycation susceptibility on kidney glomerular changes.
Urinary Liver-Type Fatty Acid–Binding Protein and Progression of Diabetic Nephropathy in Type 1 Diabetes
Authors: Panduru Nicolae M. , Forsblom Carol , Saraheimo Markku , Thorn Lena , Bierhaus Angelika , Humpert Per M. , Groop Per-Henrik ,   on behalf of the FinnDiane Study Group
Published: February 2013

OBJECTIVE

Diabetic nephropathy (DN) has mainly been considered a glomerular disease, although tubular dysfunction may also play a role. This study assessed the predictive value for progression of a tubular marker, urinary liver-type fatty acid–binding protein (L-FABP), at all stages of DN.

RESEARCH DESIGN AND METHODS

At baseline, 1,549 patients with type 1 diabetes had an albumin excretion rate (AER) within normal reference ranges, 334 had microalbuminuria, and 363 had macroalbuminuria. Patients were monitored for a median of 5.8 years (95% CI 5.7–5.9). In addition, 208 nondiabetic subjects were studied. L-FABP was measured by ELISA and normalized with urinary creatinine. Different Cox proportional hazard models for the progression at every stage of DN were used to evaluate the predictive value of L-FABP. The potential benefit of using L-FABP alone or together with AER was assessed by receiver operating characteristic curve analyses.

RESULTS

L-FABP was an independent predictor of progression at all stages of DN. As would be expected, receiver operating characteristic curves for the prediction of progression were significantly larger for AER than for L-FABP, except for patients with baseline macroalbuminuria, in whom the areas were similar. Adding L-FABP to AER in the models did not significantly improve risk prediction of progression in favor of the combination of L-FABP plus AER compared with AER alone.

CONCLUSIONS

L-FABP is an independent predictor of progression of DN irrespective of disease stage. L-FABP used alone or together with AER may not improve the risk prediction of DN progression in patients with type 1 diabetes, but further studies are needed in this regard.
Pancreatic β-Cell Dysfunction and Risk of New-Onset Diabetes After Kidney Transplantation
Authors: Zelle Dorien M. , Corpeleijn Eva , Deinum Jolijn , Stolk Ronald P. , Gans Rijk O.B. , Navis Gerjan , Bakker Stephan J.L.
Published: February 2013

OBJECTIVE

Chronic exposure to calcineurin inhibitors and corticosteroids poses renal transplant recipients (RTR) at high risk for development of new-onset diabetes after transplantation (NODAT). Pancreatic β-cell dysfunction may be crucial to the pathophysiology of NODAT and specific markers for β-cell dysfunction may have additive value for predicting NODAT in this population. Therefore, we prospectively investigated whether proinsulin, as a marker of pancreatic β-cell dysfunction, is associated with future development of NODAT and improves prediction of it.

RESEARCH DESIGN AND METHODS

All RTR between 2001 and 2003 with a functioning graft for ≥1 year were considered eligible for inclusion, except for subjects with diabetes at baseline who were excluded. We recorded incidence of NODAT until April 2012.

RESULTS

A total of 487 RTR (age 50 ± 12 years, 55% men) participated at a median time of 6.0 (interquartile range [IQR], 2.6–11.5) years after transplantation. Median fasting proinsulin levels were 16.6 (IQR, 11.0–24.2) pmol/L. During median follow-up for 10.1 (IQR, 9.1–10.4) years, 42 (35%) RTR had development of NODAT in the highest quartile of the distribution of proinsulin versus 34 (9%) in the lowest three quartiles (P < 0.001). In Cox regression analyses, proinsulin (hazard ratio, 2.29; 95% CI, 1.85–2.83; P < 0.001) was strongly associated with NODAT development. This was independent of age, sex, calcineurine inhibitors, prednisolone use, components of the metabolic syndrome, or homeostasis model assessment.

CONCLUSIONS

In conclusion, fasting proinsulin is strongly associated with NODAT development in RTR. Our results highlight the role of β-cell dysfunction in the pathophysiology of NODAT and indicate the potential value of proinsulin for identification of RTR at increased risk for NODAT.
Prepregnancy Dietary Protein Intake, Major Dietary Protein Sources, and the Risk of Gestational Diabetes Mellitus
Authors: Bao Wei , Bowers Katherine , Tobias Deirdre K. , Hu Frank B. , Zhang Cuilin
Published: February 2013

OBJECTIVE

Dietary protein is an important modulator of glucose metabolism. However, studies regarding the association between dietary protein intake and gestational diabetes mellitus (GDM) risk are sparse. This study was to examine the association.

RESEARCH DESIGN AND METHODS

Our study included 21,457 singleton pregnancies reported among 15,294 participants of the Nurses' Health Study II cohort between 1991 and 2001. Included pregnancies were free of chronic diseases before pregnancy or previous GDM. Generalized estimating equations were used to estimate the relative risks (RRs) and 95% CIs.

RESULTS

After adjustment for age, parity, nondietary and dietary factors, and BMI, multivariable RRs (95% CIs) comparing the highest with lowest quintiles were 1.49 (1.03–2.17) for animal protein intake and 0.69 (0.50–0.97) for vegetable protein intake. The substitution of 5% energy from vegetable protein for animal protein was associated with a 51% lower risk of GDM (RR [95% CI], 0.49 [0.29–0.84]). For major dietary protein sources, multivariable RRs (95% CIs) comparing the highest with the lowest quintiles were 2.05 (1.55–2.73) for total red meat and 0.73 (0.56–0.95) for nuts, respectively. The substitution of red meat with poultry, fish, nuts, or legumes showed a significantly lower risk of GDM.

CONCLUSIONS

Higher intake of animal protein, in particular red meat, was significantly associated with a greater risk of GDM. By contrast, higher intake of vegetable protein, specifically nuts, was associated with a significantly lower risk. Substitution of vegetable protein for animal protein, as well as substitution of some healthy protein sources for red meat, was associated with a lower risk of GDM.
The Effect of Prospective Monitoring and Early Physiotherapy Intervention on Arm Morbidity Following Surgery for Breast Cancer: A Pilot Study
Authors: Singh Chiara , De Vera Mary , Campbell Kristin L.
Published: February 2013

Purpose: Significant arm morbidity is reported following surgery for breast cancer, yet physiotherapy is not commonly part of usual care. This study compared the effect on arm morbidity after surgery for breast cancer of a clinical care pathway including preoperative education, prospective monitoring, and early physiotherapy (experimental group) to that of preoperative education alone (comparison group). Methods: A prospective quasi-experimental pretest–posttest, non-equivalent group design compared two clinical sites; Site A (n=41) received the experimental intervention, and Site B (n=31) received the comparison intervention. At baseline (preoperative) and 7 months postoperative, shoulder range of motion (ROM), upper-extremity (UE) strength, UE circumference, pain, UE function, and quality of life were assessed. Results: The experimental group maintained shoulder flexion ROM at 7 months, whereas the comparison group saw a decrease (mean 1° [SD 9°] vs. −6° [SD 15°], p=0.03). A lower incidence of arm morbidity and better quality of life were observed in the experimental group, but these findings were not statistically significant. Baseline characteristics and surgical approaches differed between the two sites, which may have had an impact on the findings. Conclusion: Initial results are promising and support the feasibility of integrating a surveillance approach into follow-up care. This pilot study provides the foundation for a larger, more definitive trial.
Implementation of Network-Level Falling Weight Deflectometer Survey
Authors: Chowdhury Tanveer , Shekharan Raja A. , Diefenderfer Brian K.
Published: February 2013

The Virginia Department of Transportation (DOT) has been using the results of automated video distress surveys to develop a pavement maintenance budget based on a needs assessment. However, these data consist only of quantities of distress that are visually observable at the pavement surface; no information regarding the actual structural capacity of the pavement system is available. Therefore, it is likely that maintenance activities assigned to certain locations are not the optimal treatment because of conditions unseen at the surface. Previous research conducted at the Virginia Transportation Research Council (now the Virginia Center for Transportation Innovation and Research) developed a protocol to collect data on pavement structural capacity by using the falling weight deflectometer on portions of Virginia's Interstate system. Many U.S. state departments of transportation have performed similar network surveys with the falling weight deflectometer to develop structural data for their pavements. Such data may include the deflection, effective resilient modulus of the subgrade, in situ structural number, layer moduli, overall pavement moduli, deflection basin area, modulus of subgrade reaction, area under the pavement profile, and so on. As the Virginia DOT begins the transition from using the 1993 AASHTO Guide for Design of Pavement Structures to using the Guide for Mechanistic–Empirical Design of New and Rehabilitated Pavement Structures, in situ structural characterization of the pavement network is necessary to ensure that funding spent on pavement rehabilitation is used optimally. This study presents the results of a network-level falling weight deflectometer survey of Virginia's Interstate system and describes an implementation process in which the data are used in an updated decision tree structure. The results of this study can be used by pavement design and management engineers to ensure that maintenance funding is optimally spent and to develop condition forecasting tools to assist with future funding allocations based on the structural capacity of the pavement.
Relating Ride Quality and Structural Adequacy for Pavement Rehabilitation and Management Decisions
Authors: Rada Gonzalo R. , Perera Rohan W. , Prabhakar Veena C. , Wiser Larry J.
Published: February 2013

Ride quality and structural adequacy are key pavement performance indicators. The relationship between these indicators has been a topic of frequent and continuing discussion in the pavement community, but an accepted and widely used relationship has not yet been identified. The objective of this study was to identify and verify the relationship between these two performance indicators, if any, with data from the Long-Term Pavement Performance Program. This study was meant to improve the evaluation and use of pavement condition data in pavement rehabilitation and design decisions. More specifically, it was intended to develop and document a mechanism to include values of both ride and structural adequacy within the context of current network-level pavement management system practices for highway agency implementation to ensure smooth pavements that are also structurally adequate. To accomplish the study objective, two major activities were carried out: a literature search to gather, review, and synthesize available information on relating ride quality and structural adequacy and a review and assessment of data from the Long-Term Pavement Performance Program to determine if such a relationship exists. These two activities—as well as their major findings, observations, and conclusions—are detailed; a viable relationship could not be identified.
Procedure for Optimum Pavement Deflection Test Spacings for Network-Level Applications
Authors: Carvalho Regis L. , Mustafa Endri , Stubstad Richard N. , Selezneva Olga , Briggs Robert C.
Published: February 2013

Structural models in pavement management systems range from the simple to the relatively complex. The simplest models use deflections or deflection basin parameters to characterize subgrade and pavement structural properties, while the more complex ones use pavement layer moduli (derived from deflections) and pavement layer thicknesses and material types to calculate pavement response, which is then used to predict failure, much like project-level pavement design analysis. Any pavement management system using the latter, more complex approach would undoubtedly need more defection information. In any case, deflection data collection is expensive and time-consuming. Most states and local agencies have few falling weight deflectometers, which are used mainly to collect project-level deflection data for scoping maintenance and rehabilitation work at the project level and for research purposes. This study explores the use of models to estimate the error associated with the choice of different deflection test spacings that can be used to optimize data collection for more efficient and economical applications in pavement management systems.
Use of Falling Weight Deflectometer Data for Network-Level Flexible Pavement Management
Authors: Crook Amy L. , Montgomery Sharlan R. , Guthrie W. Spencer
Published: February 2013

The objectives of this research were to investigate spatial and temporal falling weight deflectometer (FWD) testing rates employed in network-level pavement management by selected state departments of transportation (DOTs) and to recommend specific methods of FWD analysis that best reflected actual pavement conditions. With funding from the Utah DOT, a literature review and a telephone questionnaire survey were performed. FWD data collected from Legacy Parkway and Long-Term Pavement Performance Program Site 49-1001 were analyzed with models by Noureldin, Hoffman, Jameson, COST (European Cooperation in Science and Technology), Rohde, and AASHTO, as well as with multiple-layer linear elastic analysis (MLLEA), which was assumed to be the most accurate of the methods evaluated in this study. In consideration of (a) the results of two-way comparisons with the MLLEA method, (b) applicability to situations in which pavement layer thicknesses are not known, and (c) simplicity, the COST method is recommended for general implementation. To the extent that the data sets analyzed in this research are representative of the Utah DOT pavement network, the COST model should be modified according to the regression results developed in this research to produce more accurate calculations of structural number. Application of temperature corrections to FWD deflections is recommended for structural pavement monitoring.
Accounting for Material-Specific Inflation Rates in Life-Cycle Cost Analysis for Pavement Type Selection
Authors: Mack James W.
Published: February 2013

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.
Realistic Life-Cycle Cost Analysis with Typical Sequential Patterns of Pavement Treatment through Association Analysis
Authors: Pour Saeed Abdollahi , Jeong David Hyung Seok
Published: February 2013

Advancements in data collection, digital data storage, and database management technologies have dramatically increased the capabilities of state highway agencies to generate and to store highway project data. The Oklahoma Department of Transportation (DOT), along with other state DOTs, stores a large amount of highway project data throughout the life cycle of highway projects. Although much of the budget is allocated to collecting and maintaining pavement data sets, the amount of benefit from extracting information and knowledge from the data is limited. This study applies association analysis in data mining to the historical treatment data set available in the Oklahoma DOT to identify the typical sequential patterns of treatment activities. Then, a realistic life-cycle cost analysis (LCCA) model based on typical sequential patterns of pavement treatment activities is developed and compared with the traditional LCCA performed by RealCost through an example. The case study indicates that the results of the realistic LCCA can be significantly different from those of the traditional approach. Because life-cycle cost models developed in this study are based on the actual treatment strategies performed by the Oklahoma DOT, it is expected that the life-cycle cost is closer to actual costs than the traditional approach. Using the realistic LCCA model developed in this study, state DOTs will be able to develop more realistic pavement maintenance and rehabilitation strategies and budgets.
Approximation Approach to Problem of Large-Scale Pavement Maintenance and Rehabilitation
Authors: Gao Lu , Zhang Zhanmin
Published: February 2013

This study focuses on large-scale pavement maintenance and rehabilitation planning. Pavement agencies usually deal with large and diverse networks of thousands of pavement sections. The complexity of pavement maintenance and rehabilitation planning increases exponentially with the size of the network. Exact optimization methods designed for small-scale problems thus suffer from dimensionality, which significantly compromises the ability to solve such problems in a reasonable time period. Consequently, such problems should be approached from the technique of approximation. A method with the Lagrangian relaxation technique and a branch-and-cut algorithm is proposed for use as a decomposition scheme for pavement maintenance and rehabilitation planning problems when the size of the problem poses a major hurdle for its solution. The proposed approach first decomposes the network (original problem) into individual sections (subproblems) and then solves the subproblems separately. As shown in the case study, the proposed approach is able to solve problems with a practical size efficiently. More specifically, the results show that the proposed method can solve problems with a network of 1,000 sections within a reasonable time period and can yield a solution close to the optimal one.
Application of Texture Analysis and Kohonen Map for Region Segmentation of Pavement Images for Crack Detection
Authors: Mathavan S. , Rahman M. M. , Kamal K.
Published: February 2013

The first phase of a research study on detecting cracks in pavements is described. For reliable crack detection, various regions in a road image have to be segmented accurately. A procedure based on the texture and color properties of different regions of images is used in conjunction with the Kohonen map, also known as the self-organizing map. Accuracy of 89.7% was obtained with classification based on the Kohonen map of images taken with a regular digital camera and simple lighting setup. Furthermore, a complementary algorithm is described to remove spurious classifications caused by inaccuracies in the trained Kohonen map. With the help of this algorithm, an overall segmentation accuracy of 97.7% is reported. This research is expected to affect other problems in transportation engineering, such as road boundary detection and road marking inspection. The detection of cracks from the segmented regions will be addressed in the future.
Probe Vehicles Used to Measure Road Ride Quality: Pilot Demonstration
Authors: Flintsch Gerardo W. , Valeri Stephen M. , Katicha Samer W. , de Leon Izeppi Edgar David , Medina-Flintsch Alejandra
Published: February 2013

New vehicle technology is leading to efficient methods for assessing the condition of the National Highway System. The use of simple sensors such as accelerometers, installed in vehicles, could provide a cost-effective way to assess ride quality for pavement management. A pilot study compared data gathered from accelerometers with the current state-of-the-art practices for measuring ride quality. After a review of relevant previous studies involving probe vehicles, this study assessed the use of probe vehicles’ acceleration measurements to evaluate the pavement profile. The repeatability of acceleration measurements with cross-correlation and standard deviation was obtained. With visual methods and the coherence function, acceleration measurements were compared with profile measurements obtained from inertial profilers. The literature review reinforced the view that using probe vehicles for pavement condition data collection would be promising and that measuring pavement condition with typical onboard sensors could provide a cost-effective way to collect data for pavement management. Probe vehicles are most practically used in pavement management applications to describe ride quality by using vehicle accelerometers and the Global Positioning System. The pilot study confirmed that the acceleration runs were repeatable. Visual inspection of the acceleration and profile plots suggested that the acceleration profiles and smoothness measurements were similar. Analysis with the coherence function also confirmed this strong relationship. The tested methodology provides a practical way to evaluate smoothness while providing a wider base of coverage compared with that of inertial profilers.
Cracking and Rutting Performance of Composite Pavements under Testing with Heavy Vehicle Simulator: Rubberized Hot-Mix Asphalt with Gap-Graded Aggregates over Portland Cement Concrete
Authors: Wu Rongzong , Harvey John T. , Signore James M.
Published: February 2013

As part of SHRP 2, the University of California Pavement Research Center conducted two accelerated pavement tests to evaluate the effects of overlay thickness on the cracking performance of composite pavement composed of rubberized hot-mix asphalt with gap-graded aggregates and portland cement concrete (RHMA-G–PCC) by using the heavy vehicle simulator. Cracking failure mechanisms in these tests included both reflective cracking near the PCC joints and fatigue cracking in the PCC slabs. Increasing overlay thickness led to a significant increase in cracking life but at the same time increased rutting susceptibility. The data collected provide insights for design of RHMA-G–PCC composite pavements as well as calibration of related mechanistic–empirical models. The observations and findings from the two accelerated pavement test sections are summarized.
Evolution of Asphalt Mixture Stiffness under Combined Effects of Damage, Aging, and Densification under Traffic
Authors: Mateos Angel , Ayuso Javier P. , Jáuregui Belen Cadavid
Published: February 2013

The long-term evolution of asphalt mixture stiffness in the field represents a complex process in which three factors play an essential role: damage, aging, and densification under traffic. To take the factors into account adequately, not only must the level of each factor be known, but also how each level modifies the modulus of the asphalt mixture for the temperature and frequency range corresponding to field conditions. The research presented is based on experimental data from four flexible sections tested at the test track of the Centro de Estudios y Experimentación de Obras Públicas (CEDEX), in Spain. The stiffness of the asphalt layer was periodically evaluated with falling weight deflectometer back-calculation and with dynamic modulus testing in the laboratory. During a 28-month period, 1,323,600 loads were applied on the pavements. This loading caused a high level of deterioration in all sections and significant asphalt densification. The loading also provided time for some aging effects to develop. From the results of this full-scale test, different conclusions could be deduced concerning the evolution of damage, aging, and densification and how this evolution modifies the stiffness of the asphalt mixture. The effects of changes in the parameters of the original master curve have also been quantified. The model and methodology incorporated in the CalME design procedure were successfully used to reproduce the evolution of the asphalt layer modulus during the test. In particular, the assumptions of this model regarding how the dynamic modulus master curve was modified by each of the three factors were found to be valid for this experiment.
Rutting of Rubberized Gap-Graded and Polymer-Modified Dense-Graded Asphalt Overlays in Composite Pavements
Authors: Coleri Erdem , Wu Rongzong , Signore James M. , Harvey John T.
Published: February 2013

The rutting performance of polymer-modified dense-graded and rubberized gap-graded asphalt mixes used in composite pavement was evaluated with full-scale accelerated pavement testing with the heavy vehicle simulator (HVS) and laboratory test results. The effect of asphalt layer thickness on measured surface deformation for both mix types was also investigated for recommendations for future design. In addition, the progression of the rutting failure mechanism for both mix types was evaluated with transverse cross sections measured with a laser profilometer at various HVS load repetitions. The polymer-modified dense-graded mix performed better than the rubberized gap-graded mix under both laboratory and HVS testing. The greater shear movement of the rubberized gap-graded mix under HVS loading caused larger humps, which consequently increased the maximum deformation and resulted in earlier failure. Larger aggregate size and denser gradation for the polymer-modified dense-graded mix resulted in more efficient dissipation of shear stresses and created greater permanent deformation resistance.
Impact of Environmental Justice on Transportation
Authors: Amekudzi Adjo A. , Smith Mshadoni K. , Brodie Stefanie R. , Fischer Jamie M. , Ross Catherine L.
Published: February 2013

Presidential Executive Order 12898 on Environmental Justice (EJ) was signed in 1994, and the U.S. Department of Transportation (DOT) issued regulatory guidelines for addressing EJ in transportation in 1997. Transportation agencies have since adopted a range of policies, programs, and activities to identify and address disproportionately high and adverse human health and environmental effects of their policies, programs, and activities on minority and low-income populations. On the basis of the relevant literature and structured interviews, this paper assesses how state DOTs are addressing EJ issues in their decision-making processes and identifies common and effective practices. The results show that several state DOTs have implemented public involvement programs and other procedures to assess the burdens of transportation investment. However, fewer agencies assess the equity of benefits, fewer assess outcomes of EJ actions, and fewer still link EJ analysis outcomes with future funding and policy decisions. On the basis of existing practices and regulatory guidelines, the researchers formulated a performance-based, maturity-scale model that agencies can use to benchmark the effectiveness of their external and internal EJ activities in achieving EJ outcomes in transportation. The model was applied anonymously to selected agencies to demonstrate different maturity levels in addressing EJ.
Spatial Analysis of Income Disparities in Pedestrian Safety in Northern New Jersey
Authors: Kravetz Daniel , Noland Robert B.
Published: February 2013

Environmental justice regulations have proliferated in the past two decades as a method for community activists to challenge federally funded projects if they perceive that they may have a disproportionate impact on low-income communities of color. Recently, arguments have surfaced suggesting that disparities in traffic safety investments be included under the umbrella of environmental justice. This study reviewed the literature on transit-related environmental justice arguments and examined the relationship between pedestrian crashes and low-income communities of color (as well as a series of other factors). A negative binomial regression was estimated to determine whether these associations existed in a three-county area of northern New Jersey. Low median income and high black and Latino populations are two of several parameters associated with high numbers of pedestrian crashes. An innovative use was made of Street View data in recording road safety features (such as buffers, medians, and pedestrian control buttons) to examine their association with pedestrian crashes at the block group level. These features were also found to vary on the basis of the median income of each block group, although the limited amount of data precluded firm conclusions about how they affect safety. The findings suggest that there is a potential environmental justice issue regarding how pedestrian-friendly road infrastructure is distributed.
Activity-Based Travel Models and Transportation Equity Analysis
Authors: Bills Tierra S. , Sall Elizabeth A. , Walker Joan L.
Published: February 2013

The current state of practice for transportation equity analysis is moving toward the use of activity-based travel models for scenario analysis. However, little has been done to validate the use of these models for equity analysis. The first objective of this paper is to present a research framework for the equity analysis of long-range transportation plans, for the purpose of critiquing the current state of practice and pointing to key research needs. This research framework is used to identify four research areas for furthering transportation equity analysis: (a) identifying transportation priorities for different groups of interest, (b) identifying appropriate modeling tools for measuring equity outcomes, (c) identifying and analyzing equity indicators, and (d) linking the equity indicators and the transportation priorities. The second objective is to explore how well an activity-based travel demand model represents heterogeneity of travel behavior among different income classes, for the purpose of transportation equity analysis. Graphical and statistical tools are used to access how well a sample of the model data compares with a sample of travel survey data for the San Francisco Bay Area in California. The results show that although the tests of distribution equality fail, the general shape of the distributions, the central tendencies, and the relative difference of the low- versus high-income samples perform well.
Exploration of Poverty, Employment, Earnings, Job Search, and Commuting Behavior of Persons with Disabilities and African-Americans in New Jersey
Authors: Deka Devajyoti , Lubin Andrea
Published: February 2013

The extant literature that touches on the role of transportation in enhancing job accessibility for persons with disabilities has largely remained separate from the literature on the role of transportation in the job accessibility of African-Americans. Each stream focuses on either race or disability. Although a few studies have examined the combined effect of race and disability on economic outcomes, researchers have rarely examined the role of transportation. With the assertion that transportation issues for minority populations and persons with disabilities are often similar, this study encompassed race, disability, economic well-being, and transportation. Taking New Jersey as the study area, the study examined how disability and race are related to employment, poverty, and earnings and how the commuting and job-search behavior of persons with disabilities is affected by their race. Statistical models clearly show that both disability and race are strongly associated with economic well-being. Analysis also shows that African-American persons with disabilities are far more likely to use public transit than non-African-Americans with disabilities. The commuting patterns of workers in the state also indicate that fewer African-Americans have jobs in close proximity to their homes than those of other races, regardless of disability. The policy implications of these findings are discussed.
Influences of Neighborhood Crime on Mode Choice
Authors: Ferrell Christopher E. , Mathur Shishir
Published: February 2013

It is understood that the threats posed by possible criminal activity in a neighborhood can play a major role in the decision to drive, take transit, walk, or ride a bicycle, but little empirical evidence has yet been gathered to support this notion, let alone guide public infrastructure investments, land use planning, or the allocation of police services. This study found that high-crime neighborhoods tend to discourage residents from walking or riding a bicycle. When a high-crime neighborhood is compared with a lower-crime neighborhood, the odds of choosing walking over driving decrease by 17% for work trips and 61% for nonwork trips. However, transit trips appear to respond to neighborhood crime in a way similar to auto trips; that is, high-crime neighborhoods appear to encourage transit use. The odds of choosing transit over the auto increase by 17% for work trips and 164% for nonwork trips. The study found that transit access trips (walking, bicycling, or driving to a transit station) are sensitive to neighborhood crimes in keeping with theoretical expectations: high-crime neighborhoods discourage walking and bicycling and encourage driving to transit stations. Specifically, for transit access to work trips, the odds of choosing to walk or bike to a transit station instead of driving decrease by 48%.
Decomposing Young Germans’ Altered Car Use Patterns
Authors: Kuhnimhof Tobias , Wirtz Matthias , Manz Wilko
Published: February 2013

Since the turn of the millennium, car ownership and car travel among young German adults have decreased noticeably. This paper analyzes these changes in young Germans’ mobility behavior on the basis of a mobility diary survey and an income and expenditure survey. The decrease in car travel by young adults is linked to lower car ownership in this group. However, behavioral changes among car owners are far more important with regard to their overall decrease in car travel. Logistic regression was applied to identify the attributes of young households that are associated with low and altering car ownership. This model indicated that structural changes in the population concerning income, employment, household composition, and residential location account for the majority of the decrease in car ownership among young households. However, the model also showed that, all things being equal, the probability of car ownership has changed. Specifically, the gender gap for car ownership has almost disappeared because young men are less likely to own a car today than in the 1990s. The study also investigated changes in car use by car owners. The results showed that men have reduced their total travel and that both men and women have reduced their car mode share and exhibit increasingly multimodal behavior.
Heterogeneity in Correlates of Motorized and Nonmotorized Travel in Germany
Authors: Procher Vivien , Vance Colin
Published: February 2013

Drawing on individual-level mobility data from Germany between 1996 and 2009, this analysis econometrically investigates the determinants of automobile, public transit, and nonmotorized travel. The paper explores whether gender plays a role in determining the relative use of motorized and nonmotorized modes and, if so, how this role is mitigated or exacerbated by other socioeconomic attributes of the individual and the household. The results indicate that women display a relatively higher use of public transit and nonmotorized modes coupled with a lower use of the car. However, it is important to qualify conclusions on the effect of gender, given the range of confounding factors that mediate its impact, including age, the presence of children, the proximity to public transit, and the commute distance. The econometric estimates indicate that fare pricing and infrastructure provision have a significant influence on how individuals reach mode allocation decisions and that women, in particular, stand to benefit from the maintenance of an efficient and dense public transportation network.
Attracting Students to Transportation Engineering
Authors: Ivey Stephanie S. , Golias Mihalis M. , Palazolo Paul , Edwards Stephen , Thomas Patrice
Published: February 2013

With a significant fraction of the nation's transportation workforce nearing retirement age, it is essential to attract new talent to transportation fields and to retain that talent. In addition, it is also important to attract a diverse workforce, because women and minorities are still significantly under-represented in transportation engineering and related fields. To address the nation's transportation workforce needs, FHWA, the U.S. Department of Transportation, the Institute of Transportation Engineers, and other leading transportation organizations emphasize the importance of outreach activities in kindergarten through 12th grade. In particular, programs directed at middle and high school students are essential for increasing the pipeline of transportation students and professionals. One such program at the University of Memphis in Tennessee, Transportation Engineering Careers (TREC), is designed to increase high school students’ interest in transportation careers through a week-long, fast-paced, active learning environment. This paper first provides a review of relevant literature and then presents assessment findings from the first 2 years of the TREC program regarding gender differences and student perceptions of transportation engineering. Finally, lessons learned and implications for similar efforts are also presented.
Exploring the Service Needs of Pregnant Air Passengers
Authors: Chang Yu-Chun
Published: February 2013

Several studies have found that women in good health are able to fly without concern for safety at any point before the 36th week of pregnancy. However, air transportation facilities and services are designed for general passengers and seldom consider the service needs of pregnant women. To understand the pregnant traveler's wants and needs, this study examined the perception of and satisfaction with air transportation services in a sample of female air passengers who boarded international flights during pregnancy. The results showed that the performance of service attributes, such as seat selection, user-friendly onboard restrooms, and assistance in boarding the aircraft, did not meet the respondents’ expectations. It was also found that the service needs of women less than 6 months pregnant differed from those of women more than 6 months pregnant.