North Carolina Department Of Transportation Research Articles

Sigmoidal Models for Predicting Pavement Performance Conditions

AbstractThis study presents an approach to develop sigmoidal family pavement performance models (pavement performance ratings versus pavement age) for a pavement management system (PMS). Pavement condition data collected from windshield surveys oftentimes suffer quality issues stemming from human subjectivity, and pavement age sometimes not being properly reset after a treatment. These issues can be systematically addressed by the proposed approach, and nonlinear sigmoidal family performance models can then be developed using the cleaned condition data. In a case study, this approach was successfully applied to a sample data set extracted from the North Carolina Department of Transportation (NCDOT) PMS. Contour plots developed for the raw data and the cleaned data showed that the data cleansing process was effective. Goodness-of-Fit indicators and cross-validation suggest that the resulting nonlinear sigmoidal models fit the condition data well.

Factors Affecting Sediment Basin Efficiency on Highway Construction Sites in the Piedmont Region of North Carolina

Sediment basins are a commonly used best management practice on North Carolina Department of Transportation (NCDOT) highway construction sites for capturing entrained sediment during stormwater runoff events. The NCDOT currently uses a sediment basin design that has a volume proportional to the disturbed catchment area and a surface area proportional to the 10-year peak runoff discharge from the catchment. This project monitored four active NCDOT sediment basins in the Piedmont region of North Carolina to evaluate several hydrologic and land use parameters for their ability to explain the variability of turbidity and total suspended solids (TSS) entering the basins as well as the efficiency of the basins with regard to these two parameters. TSS ranged from 270 to 53,000 mg L -1 entering the basins and from 87 to 70,600 mg L -1 leaving the basins. Turbidity ranged from 198 to 29,000 nephelometric turbidity units (NTU) entering the basins and from 27 to 28,700 NTU leaving the basins. There was no clear relationship between the stages of development or site activities and the turbidity and TSS entering the basins. Peak flow, which is used in the design of NCDOT sediment basins, was positively correlated with inlet turbidity and TSS. Additionally, the performance of the basins to reduce turbidity and TSS did not correlate to storm characteristics. The diversion ditches leading to the basins appeared to be a major source of sediment and likely contributed to the high variability in turbidity, TSS, and basin performance.

Benefit-cost Methodology for Highway-railway Grade Crossing Safety Protocols as Applied to Transportation Infrastructure Project Prioritization Processes

This paper summarizes efforts in assisting the North Carolina Department of Transportation (Rail Division) in developing a methodology for identifying and prioritizing safety projects at highway-rail at-grade crossings (grade crossings). This approach leverages recent developments in data management to improve the identification, prioritization and selection of safety projects through the calculation of all the costs and benefits associated to a safety project. This approach will also provide policymakers with the kind of information they need to communicate with the public and other government agencies about the benefits of investing in safety.

Using Mobile Phone Location Data to Develop External Trip Models

This paper explores the use of passively collected data on the location of mobile phones in the development of external travel models, which capture trips to, from, and through an area. The data were collected 24 h a day for 1 month during May 2013 for the North Carolina Department of Transportation. The data cover the French Broad River Metropolitan Planning Organization and surrounding counties in North Carolina. This paper details the format of the data collected and the required processing and cleaning to support the development of the external trip models. The process for developing a through-trip table and estimating external trip interchanges in the region is presented, along with validation techniques for both. The results of this effort show that passively collected mobile phone data can be a good source of local information for developing external trip models.

Nonmotorized Site Selection Methods for Continuous and Short-Duration Volume Counting

This paper outlines the process for selecting sites to perform counts on transportation facilities in the context of establishing a nonmotorized traffic volume counting program. Many agencies are well practiced in collecting motor vehicle traffic counts and estimating annual average daily traffic volumes for motor vehicles on the basis of knowledge founded on years of research and experience. Selecting sites is one component of developing a consistent system for quantifying nonmotorized travel so bicycle and pedestrian volumes can ultimately feed into tools to measure existing trends and model future increases in nonmotorized trips at site, corridor, and regional levels. The outcome of collecting count data can ultimately assist in evaluating facility usage over time, better inform the project prioritization process, and provide evidence to support nonmotorized facility inclusion through Complete Streets planning and improve planning for active transportation. This paper outlines the goals of a nonmotorized traffic monitoring program and objectives of the site selection process. From the experience of a pilot project conducted by the North Carolina Department of Transportation, the site selection method details the following components: gathering potential sites, conducting a site visit, gathering additional data needed to inform the decision-making process, and ultimately selecting sites and developing an equipment inventory.

Thermal Cracking of Mass Concrete Bridge Footings in Coastal Environments

The North Carolina Department of Transportation (NCDOT) identified several mass concrete footings in coastal bridges with cracking that needed to be assessed in the context of current North Carolina mass concrete specifications. Cracked concrete in coastal environments is of particular concern due to the higher potential for corrosion damage. Site visits were made to assess the extent of the cracking observed in mass concrete footings of three different bridges. A finite-element model was developed and used to analyze the footings and assess them for their early age thermal cracking potential. Finite-element model results showed that reasonably sized mass concrete footings that followed typical NCDOT control plans did not have a high likelihood of significant cracking from thermal stresses. However, a much larger mass concrete footing had a distinctly higher risk of significant cracking even when typical NCDOT control plans are followed. Further, cracking was even more likely when formwork was removed early. The model results correlated well with observations from the field. A comparison with temperature rise results from the Schmidt method, as implemented in the design of the mass concrete structural elements, shows the Schmidt method’s limitations in predicting temperature differences for very large mass concrete footings.

Cost-Effectiveness Sketch Method for Safety Investment Decision Making

The recent Moving Ahead for Progress in the 21st Century Act emphasizes a performance-based, outcome-driven planning process to meet performance targets. One area of performance-based planning highlighted by the legislation is safety planning. State departments of transportation and metropolitan planning organizations will be required to document how their strategic highway safety plan supports the state safety performance targets. Currently, for safety improvements to be maximized for every dollar of investment, a cost-effectiveness analysis is used within subdisciplines of safety planning but is rarely used to compare projects across the four Es of safety: engineering, education, enforcement, and emergency medical services. A sketch method is proposed for analyzing cost-effectiveness of safety investment decision making across the four Es. The sketch-level method is appropriate when quantitative project information, such as crash reduction effectiveness, target population, and duration of project effectiveness are unavailable or are not complete. The sketch method results in multidisciplinary safety investments grouped by their relative cost-effectiveness; this method allows practitioners to use this information to prioritize investments for implementation. Results from a demonstration application of the sketch method to safety projects provided by the North Carolina Department of Transportation are presented.

Preliminary Results towards Developing Thresholds for Pavement Condition Maintenance: Safety Perspective

This paper focuses on examining the relationship between the International Roughness Index (IRI) and crashes to compare thresholds from a safety perspective with fuel efficiency perspective and pavement condition categories. Findings from the literature review, profile elevations captured using a laser profilometer along two test corridors in the State of North Carolina, United States (first one with concrete pavement and the second one with asphalt pavement), traffic volume from travel survey maps, and crash data maintained by the North Carolina Department of Transportation (NCDOT) were used for analysis and identification of preliminary thresholds from the safety perspective for pavement maintenance. Profile elevation data was processed to compute IRI values for each 100-m (330-ft) section along each selected corridor by direction. Crashes (all and under wet-pavement conditions) were identified for each section and added to the database. Scatter plots were generated to observe the trends in the number of all and wet-pavement crashes per mile by IRI. The average number of all crashes per section, wet-pavement crashes per section, all crashes per million vehicle miles travelled (MVMT) and wet- pavement crashes per MVMT were also computed for each corridor. Results obtained indicate that targeting and maintaining lower IRI to improve fuel efficiency may yield similar benefits from a safety perspective. Based on analysis using data for the considered corridors, they do not seem to vary by pavement type.

Compensatory Stream and Wetland Mitigation in North Carolina: An Evaluation of Regulatory Success

Data from a probability sample were used to estimate wetland and stream mitigation success from 2007 to 2009 across North Carolina (NC). "Success" was defined as whether the mitigation site met regulatory requirements in place at the time of construction. Analytical results were weighted by both component counts and mitigation size. Overall mitigation success (including preservation) was estimated at 74% (SE=3%) for wetlands and 75% (SE=4%) for streams in NC. Compared to the results of previous studies, wetland mitigation success rates had increased since the mid-1990s. Differences between mitigation providers (mitigation banks, NC Ecosystem Enhancement Program's design-bid-build and full-delivery programs, NC Department of Transportation and private permittee-responsible mitigation) were generally not significant although permittee-responsible mitigation yielded higher success rates in certain circumstances. Both wetland and stream preservation showed high rates of success and the stream enhancement success rate was significantly higher than that of stream restoration. Additional statistically significant differences when mitigation size was considered included: (1) the Piedmont yielded a lower stream mitigation success rate than other areas of the state, and (2) recently constructed wetland mitigation projects demonstrated a lower success rate than those built prior to 2002. Opportunities for improvement exist in the areas of regulatory record-keeping, understanding the relationship between post-construction establishment and long-term ecological trajectories of stream and wetland restoration projects, incorporation of numeric ecological metrics into mitigation monitoring and success criteria, and adaptation of stream mitigation designs to achieve greater success in the Piedmont.

Blueprint for Sustainability

An increasing number of transportation agencies in the United States are using sustainability as a device to frame transportation decision making and to demonstrate performance-based accountability. Despite interest in sustainability as an organizing concept for transportation decision making, the practice in which sustainability is used to frame formal policy development at state departments of transportation is still in its formative stages. This paper presents the approach that the North Carolina Department of Transportation (DOT) has taken to adopt sustainability as an agency value. Currently in the implementation phase, the department's blueprint for sustainability is not a stand-alone plan, but rather a set of principles, objectives, performance measures, and strategies that have been integrated into the overall strategic direction and policy framework of the North Carolina DOT. The process used to create this product has relied on a combination of internal and external outreach, agency introspection, and conversations with senior leadership to conceptualize sustainability in a way that resonates within the agency's culture and context. A variety of lessons, including the importance of flexibility, integration, and strategic coordination with related agency initiatives, can be derived from this process. Through the presentation and the evaluation of the process that the North Carolina DOT uses, this paper provides transportation practitioners with useful insights into how to integrate sustainability as an agency value and a decision-making framework.

Summit Discusses Public Health Implications of Fracking

Summit Discusses Public Health Implications of Fracking

Public Opinions of Roadway Assets

In October 2011, the North Carolina Department of Transportation conducted a roadway review with a randomly recruited sample of North Carolina residents and community leaders. More than 300 people from 61 communities participated in the surveys, which were held in six locations: Asheville, Burlington, Charlotte, Jonesville, Rocky Mount, and Wilmington. The purpose of the roadway review was twofold: to determine the expectations for the condition of North Carolina highways and to identify the features that North Carolinians believe are most important on different types of highways. Surveys were completed during both daytime and nighttime hours and covered many roadway maintenance aspects, such as pavement, landscaping and mowing practices, signage, retroreflectivity, and shoulders. Regression equations are also provided to predict the overall satisfaction of condition, safety, and appearance by each individual roadway type.

Safety Effectiveness of “Vehicle Entering When Flashing” Signs

This project evaluated the safety effectiveness of “Vehicle Entering When Flashing” (VEWF) intersection conflict warning systems (ICWSs) at stop-controlled intersections. The North Carolina Department of Transportation has utilized this treatment, which consists of vehicle-actuated sign and flasher assemblies placed at or near the intersection to warn motorists on the major or minor road, or both, of vehicles entering the intersection. Although this countermeasure has been used for years in North Carolina, and similar ICWSs have been used in other states, there has been minimal safety evaluation to prove or validate the systems' effectiveness. This study evaluated four categories of VEWF systems. Sites were categorized on the basis of the direction of the alert and placement from the intersection. Crash modification factors (CMFs) were provided for all sites and each category, as well as exclusively for sites with two-lane at two-lane intersections. Empirical Bayes before-and-after techniques were used to overcome the regression to the mean threat. Deployments with major road alerts in advance of the intersection and a combination of both major and minor road alerts were determined to be most effective for two-lane at two-lane stop-controlled intersections with CMFs for total crashes of 0.68 and 0.75, respectively.

Safety Evaluation of Discontinuing Late Nighttime Flash Operations at Signalized Intersections

This study examined the safety impacts of converting late nighttime flash operation to normal phasing operation at signalized intersections by using the empirical Bayes, the univariate full Bayes, and multivariate full Bayes before-and-after methods. Data were obtained from the North Carolina Department of Transportation for 61 treatment sites and 395 reference intersections that remained on late nighttime flash operation from 2000 to 2007. The results from the empirical Bayes method are almost identical to those of the univariate full Bayes. The full Bayes method offered more flexibility in selecting the functional form of expected crashes at similar sites (similar to the safety performance function in the empirical Bayes) and in addressing uncertainty in the data. Compared with the univariate full Bayes, the multivariate full Bayes with the multivariate Poisson lognormal (MVPLN) model provided better results based on much lower deviance information criterion values. The MVPLN model was favored and the recommended crash reduction factors are 48% (±6%), 53% (±8%), and 57% (±7%) for nighttime total, injury and fatal, and frontal impact crashes, respectively.

Degradation Modeling of Polyurea Pavement Markings

Polyurea is a long life, quick-curing material used in pavement markings and a material of interest to the North Carolina Department of Transportation. This article presents a performance model and the characteristics of polyurea pavement markings in North Carolina by using Ordinary Least Squares models. The performance-based models provide pavement marking managers with tools to better allocate limited manpower and resources to optimize budgets while maintaining newly proposed pavement marking retroreflectivity levels of service. This research constructed performance models for polyurea pavement markings based on the independent variables of time, initial retroreflectivity, lateral line location, and annual average daily traffic. Using the models generated by this research, pavement marking managers can predict the remaining life of a given pavement marking to maintain a standard level of service. A key finding of this article is that the type of glass bead used in the marking significantly affects polyurea pavement marking degradation.

EMF1 A GIS Evaluation of a Statewide EMS Stroke Routing Protocol on Community Hospital Bypass for Acute Stroke Patients

Background: On January 1st, 2010, the North Carolina (NC) Office of Emergency Medical Services (EMS) implemented an out-of-Stroke Triage and Destination Plan (STDP) for patients with suspected acute stroke. The STDP requires that EMS providers categorize destination hospitals as being a community hospital (CH), a Stroke Capable Hospital (SCH) or a Joint Commission Certified Primary Stroke Centers (JCCPSC). The STDP specifies that, within certain constraints, hospitals unable to routinely provide IV tissue plasminogen activator (CH) should be bypassed for patient transport to hospitals with that capability (SCH or JCCPSC). Study Objective: To determine if the STDP increased the frequency of CH bypass by EMS when transporting patients with an out-of-hosptial impression of acute stroke with the following time constraints: ability to be transported to a SCH or a JCCPSC within 2 hours from symptom onset, and with a transport time not exceeding 50 minutes. Methods: Utilizing a before-after design, geographical information system (GIS) analytical methods, and a statewide Prehospital Medical Information System database, we identified patients with a suspected acute stroke who accessed EMS within 120 minutes of symptom onset. We compared two time periods: the 12 months immediately before implementation of the STDP and the 12-month period beginning 3 months after STDP implementation. We geocoded incident and hospital addresses using Esri ArcGIS software and other available source data, including address points and/or NC Department of Transportation (DOT) Integrated Statewide Road Network (ISRN). We used Esri Network Analyst software and NC DOT ISRN data to determine the closest acute care hospital to stroke incident locations. We then identified cases in which EMS bypass of a community hospital within the specified time constraints was an option and determined if bypass occurred. Chi square analysis was used to compare the pre- and post-STDP periods. Results: We identified 2,624 patients with a symptom onset 120 minutes from EMS arrival, an out-of-hospital impression of acute stroke, and a geocodable scene address with a community hospital as the closest acute care hospital. Of those patients, 43% (n=1141) were in the pre-STDP period, while 57% (n=1483) were in the post STDP period. Preliminary results indicate that a community hospital was bypassed 52% of the time in the pre-STDP period and 50% of the time in the post-STDP period. At the time of abstract submission, it was not yet known how many of these cases met the specified time constraints of the STDP. Sensitivity analyses are ongoing to determine the comparability of patients in each of the study periods. Conclusion: Our preliminary results suggest that the STDP had no impact on the rate of EMS bypass of community hospitals for patients with suspected acute stroke. Final results will be presented at the 2012 ACEP Research Forum.

The North Carolina Department of Transportation’s Vision for Healthy Communities Through Sustainable Transportation

The North Carolina Department of Transportation increasingly includes the health of North Carolinians in its transportation decision-making. With an expanded mission that now includes health, the agency is integrating public health considerations into its initiatives, plans, and policies, as well as exploring the use of health impact assessments.

Running the Numbers

This article summarizes statistics regarding pedestrian crash injuries in the state of North Carolina. This authors report characteristics of the pedestrian–motor vehicle crashes that were reported statewide for the 5-year period from 2007-2011, and include age, sex, and race/ethnicity of the people involved in the crashes, temporal and environmental factors, and type of roadway. Data used are from the Division of Motor Vehicles Crash Database, North Carolina Department of Transportation, a database of police crash reports. The authors present data from all crashes classified as reportable pedestrian crashes (those that involve greater than $1,000 in property damage and/or a personal injury), and include all road types (ie, state and local maintained roads). The authors note that pedestrian crashes tend to be especially serious. During this 5-year interval, more than 9% of pedestrians struck by a motor vehicle in North Carolina were killed, whereas the fatality rate for all crash-involved people (mostly drivers and passengers) was only 0.3% over the same time period. The authors conclude with a section of recommendations for improving pedestrian safety, including the use of engineering countermeasures and street redesign, as well as safety-related programs. Readers are referred to a new pedestrian safety campaign called Watch For Me NC (http://www.watchformenc.org).

Short‐Term Impacts of a 4‐Lane Highway on American Black Bears in Eastern North Carolina

Short‐Term Impacts of a 4‐Lane Highway on American Black Bears in Eastern North Carolina

Use of “Your Speed” Changeable Message Signs in School Zones

The Safe Routes to School (SRTS) program, through a variety of tools, seeks to enable children to walk and bicycle safely to school. One such tool recently implemented through a program of the North Carolina Department of Transportation (DOT) is the use of speed feedback signs (“Your Speed” signs) to reduce vehicle speeds in school zones. The North Carolina DOT has no policy or standard for the use of these signs within school zones, and research illustrating the value of using permanently installed “Your Speed” signs in school zones is sparse. The Eastern Carolina Injury Prevention Program (ECIPP) applied for SRTS funding to install these signs as part of its education, encouragement, and enforcement project. The North Carolina DOT therefore initiated a study on the use of the signs in conjunction with ECIPP's larger SRTS project. Significant findings of this study include a 3.0 mph (p < .0001) to 4.5 mph (p < .0001) reduction in speed sustained over a 12-month postinstallation period, suggesting that responses to “Your Speed” signs may not diminish as drivers become accustomed to the signs’ presence. On the basis of these promising results, the North Carolina DOT is considering additional research to inform policy considerations fully for the future use of such signs. This research may be useful for organizations seeking innovative SRTS program tools to improve speed compliance in school zones, contemplating the use of speed feedback signs in school zones but needing information on their effectiveness, and having interest in a different way to evaluate their own SRTS projects.