Institute for Transportation

About the research

The main objective of this synthesis was to identify and summarize how agencies collect, analyze, and report different work-zone traffic-performance measures, which include exposure, mobility, and safety measures. The researchers also examined communicating performance to the public. This toolbox provides knowledge to help state departments of transportation (DOTs), as well as counties and cities, to better address reporting of work-zone performance.

About the research

The goal of this project was to provide an objective methodology to support public agencies and railroads in making decisions related to consolidation of at-grade rail-highway crossings. The project team developed a weighted-index method and accompanying Microsoft Excel spreadsheet based tool to help evaluate and prioritize all public highway-rail grade crossings systematically from a possible consolidation impact perspective.

Factors identified by stakeholders as critical were traffic volume, heavy-truck traffic volume, proximity to emergency medical services, proximity to schools, road system, and out-of-distance travel. Given the inherent differences between urban and rural locations, factors were considered, and weighted, differently, based on crossing location. Application of a weighted-index method allowed for all factors of interest to be included and for these factors to be ranked independently, as well as weighted according to stakeholder priorities, to create a single index. If priorities change, this approach also allows for factors and weights to be adjusted.

The prioritization generated by this approach may be used to convey the need and opportunity for crossing consolidation to decision makers and stakeholders. It may also be used to quickly investigate the feasibility of a possible consolidation. Independently computed crossing risk and relative impact of consolidation may be integrated and compared to develop the most appropriate treatment strategies or alternatives for a highway-rail grade crossing. A crossing with limited- or low-consolidation impact but a high safety risk may be a prime candidate for consolidation. Similarly, a crossing with potentially high-consolidation impact as well as high risk may be an excellent candidate for crossing improvements or grade separation.

The results of the highway-rail grade crossing prioritization represent a consistent and quantitative, yet preliminary, assessment. The results may serve as the foundation for more rigorous or detailed analysis and feasibility studies. Other pertinent site-specific factors, such as safety, maintenance costs, economic impacts, and location-specific access and characteristics should be considered.

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About the research

Rutting, caused by a depression or groove of traveling wheels worn into a road, is a major problem of conventional asphalt or flexible pavements, and is primarily due to plastic deformation of the asphalt concrete near the pavement surface. To overcome this problem, a hybrid, made with asphalt (flexible) pervious concrete filled with Portland cement (rigid) mortar, called casting cement asphalt mixture (CCAM), has been developed.

During the development process, various CCAMs were made with Iowa concrete materials. Experiments were conducted to gauge optimal porosity of asphalt pervious concrete and optimal flowability of mortar for CCAMs. The basic engineering properties of these CCAMs, such as strength, shrinkage, and freeze-thaw durability, were evaluated.

The results show that CCAMs can be produced successfully by using pervious concrete of 25% porosity and rapid set cement grout with very high flowability. The calcium sulphoaluminate cement grout used in this study attained strength greater than 18 MPa (2,600 psi) in less than 12 hours. Therefore, a CCAM pavement could open to traffic at a much earlier time than a conventional Portland cement concrete roadway. While asphalt concrete displayed a 9 mm rut after being subjected to 10,000 wheel track cycles during a wheel track rutting test, the CCAM showed a less than 1 mm rut. However, as the CCAM is neither asphalt nor Portland cement concrete, a big project challenge was to find appropriate test methods for evaluating key properties of CCAM, especially the method for testing its freeze-thaw durability.

Although CCAM has attracted a great deal of attention in Europe and Asia, most applications have been in warm climate regions. Few applications of CCAM have been conducted in the US, especially in cold climate regions. Further investigation needs to be done on the CCAM freeze-thaw durability before this new material is applied to Iowa pavements.

Funding Sources:
Iowa Department of Transportation
Iowa Highway Research Board ($45,000.00)
Mid-America Transportation Center
USDOT/OST-R
Total: $45,000.00

Contract Number: DTRT13-G-UTC37

About the research

This project investigated regulatory issues that may affect or limit freight movement in Iowa and other Midwest states: Illinois, Iowa, Kansas, Minnesota, Missouri, Nebraska, South Dakota, and Wisconsin. Current state regulations for the following are reviewed and summarized:

• Vehicle dimensions
• Vehicle weights
• Driver qualifications
• Enforcement
• Fees and taxes
• Medical certification
• Hours of service
• Oversize-overweight permits

About the research

To facilitate a region’s freight transportation systems planning and operations and minimize the risk associated with increasing multimodal freight movements, this study presents a modeling framework for evaluating and optimizing freight flows on a multimodal transportation network under disruption. Unexpected events such as earthquakes, floods, and other manmade or natural disasters would cause significant economic losses. When parts of the transportation network are closed or operated at a reduced capacity, the delay of commodity movements would further increase such losses. Shifting to an alternative route or mode might help to mitigate the negative impacts. In this study, a multimodal freight transportation network was developed to simulate commodity movements, evaluate the impacts of disruptions, and develop effective emergencyoperation plans. A fluid-based dynamic queuing approximation was used to estimate the delays at classification yards and locks caused by disruption. Using the Federal Highway Administration’s (FHWA) Freight Analysis Framework version 3 (FAF3) database, a case study was constructed to model the transportation of cereal grains from Iowa to other states. Three hypothetical disruption scenarios were tested: a reduced service level at locks along the Mississippi River, a bridge outage on I-80 at the Missouri River, and severe weather in central Iowa closing the Union Pacific tracks in the area. The impacts of these disruptions were quantified and analyzed using the presented freight network model.

About the research

A significant amount of time and effort is invested to collect and document various field activity data of a highway project in Daily Work Report (DWR). Although there are many potential benefits of DWR data, the current use of the data is very limited. The objective of this study is to develop an ideal framework for an advanced DWR system to improve the DWR data collection and utilization practices. A literature review and two surveys were conducted to investigate the current practices of collecting DWR data, utilization of the data, and challenges associated with advanced collection and utilization of DWR data. The study found that there is a huge gap between the current and potential level of benefits of DWR data. The challenges for better collection and utilization of DWR data were identified and classified. An ideal framework for an advanced DWR system was developed to overcome those challenges. The ideal framework consists of seven major components: a) data attributes and its relations, b) integration with existing systems, c) visualization of data, d) advanced data collection systems, e) automation of DWR data analysis and reporting, f) human factors, and g) other technical aspects. The framework can be used by state DOTs to improve an existing DWR system or to develop a new system. The implementation of the framework is expected to improve the level of DWR data collection and utilization practices in state DOTs.

About the research

The final report presents the results of an experimental and computational study on the recently-developed air-coupled impact-echo (IE) nondestructive testing (NDT) method, in which microphones replace the traditional physically-coupled IE sensors. To develop an optimum testing system and verify the new method, two concrete plates were tested in the laboratory, one of which was a solid concrete slab, and the other was a mock-up reinforced concrete bridge deck with artificial defects. An IE testing system was developed using a custom program written in LabVIEW. The accuracy and feasibility of the air-coupled test method to determine the solid thickness of concrete structures and to detect defects or flaws, such as delaminations or voids, were verified by comparing test results obtained via the air-coupled and physically-coupled sensors. When using the air-coupled IE method in practice, ambient noise generated by wind, traffic, and machinery will be sensed by the microphones and therefore reduce the signal to noise ratio of the data. Additionally, a portion of the acoustic energy generated by the impacts during testing will be lost due to the mismatch in acoustic impedance between concrete and air. To address these problems, a parabolic reflector and a sound isolation enclosure were studied and found to improve the quality of recorded signals compared to using a microphone alone. Finite element method (FEM) based numerical simulations were conducted using COMSOL Multi-physics software to understand the mechanics of the air-coupled IE test, determine the optimum geometry for the parabolic reflector, and investigate the effects of the microphone height. Signal filtering techniques including band-pass, high-pass, and adaptive filters were implemented in MATLAB for post-processing the test data. High-pass filters were found useful for minimizing measured ambient traffic and wind noise, which was determined to be primarily below 2 kHz. Two-dimensional (2D) IE scanning tests were conducted on the bridge deck with artificial defects to locate the defect positions by the air-coupled and physically coupled test methods. Results obtained by these two methods are in good agreement, demonstrating the accuracy and feasibility of the air-coupled IE test method.

About the research

Bridge condition inspection data provide critical and rich information for assessing structural condition. Currently, the majority of bridge inspection methods use printed checklists, and their interpretation is labor intensive, subject to personal judgment, and prone to error. To realize the full benefits of bridge inspections, there is a need to automate the data management process. This research project implemented Bridge Information Modeling (BrIM) technology for bridge inspections and compared it to the conventional approach of paper checklists. This environment combines a 3D representation of the infrastructure, and allows the integration of inspection data, such as the presence of damages, types of damages, severity, localization and previous maintenance decisions. In this report, BrIM acronym is used to refer to the database that integrates a 3D bridge model and bridge element condition data. In order to validate this approach, 2D drawings and previous inspection and maintenance data of two bridges located in Ames, Iowa were obtained and modeled using Revit software. Both models were then synced using cloud based solutions so that they could be accessed from tablet computers on-site. Then, the BrIM based inspection methodology was tested with Iowa DOT engineers and bridge inspectors, who confirmed that BrIM would be beneficial to automatically query, sort, evaluate and send information to decision makers. Furthermore, a web-based survey with several DOT engineers and bridge inspectors was conducted regarding possible expected benefits of using 3D BrIM based solutions for inspections. It is concluded that this methodology has the potential to substantially improve bridge assessment and maintenance operations, which would result in time and cost savings associated with bridge inspection and assessment, as well as improved structural resiliency as a result of more effective and comprehensive bridge management means.

About the research

With ever-tightening budgets, states are looking for cost-effective methods of lengthening the time from initial bridge construction to its complete replacement. One common technique to make effective use of funds and to minimize the time from initial construction to replacement is to replace the deck after it has reached the end of its useful service life while keeping the original superstructure and substructure (assuming that the superstructure and substructure still have adequate strength and remaining life). However, one key element to such a deck replacement is ensuring that the deck is removed successfully without damaging the superstructure elements. The situation is especially important/difficult when the deck must be removed in large pieces without allowing concrete to fall under the bridge.

Contractors are typically using saws to segment the deck and impact equipment (breakers, chipping hammers, etc.) to then break the deck segments free from the superstructure elements. There are attributes of both steel and concrete (prestressed) girders that present difficulties in such operations. For example, steel girder bridges have a variety of shear connector types (sometimes with variable spacing) and are quite susceptible to top flange cutting; current standard concrete girders have very thin top flanges that make them vulnerable to impact and other damage.

When damage to the superstructure occurs, delays in reconstruction can be quite significant.  Recent examples can be found in many locations across the US. More efficient and reliable methods for concrete deck removal are needed.

The objective of this work is to determine and/or develop new cost-effective and efficient deck removal techniques for steel superstructure bridges. The following criteria will be considered as part of the evaluation:

• Impact on the future performance of the superstructure
• Cost – including cost comparison between deck removal and complete superstructure replacement
• Time
• Safety
• Noise

Furthermore, the work proposed herein will include guidance on assessing and repairing steel girders that are damaged during removal of a deck.

About the research

The majority of crash fatalities in the United States occur along rural roadways. These roadways typically have low volumes and widespread crashes. In other words, no one location generally has an unexpectedly high number of crashes. Systemic safety tools/methodologies can be used in this type of situation because they evaluate and prioritize expected crash risk through the consideration regional data patterns, research results, and engineering judgment. This project investigated two systemic safety tools/methodologies:  the approach followed to produce Minnesota county road safety plans (and now described in the FHWA Systemic Safety Project Selection Tool) and usRAP. Both tools/methodologies were applied with data collected from two counties in Iowa and a sensitivity analyses completed on their results. It was concluded that changing the “weight” of the safety risk factors considered as part of Minnesota approach could have an impact on some of the locations in the “top 20” of the rankings and subsequent decision-making. However, the amount of that impact varied and a correlation analysis of the original and alternative rankings developed found a statistically insignificant difference. The change in acceptable benefit-cost ratio for the application of usRAP showed that it impacted the type and number of countermeasures, along with the benefit-cost ratio of the plan suggested by the software. It is recommended that additional research be completed to consider similar input variable changes on transportation systems with a higher level of variability in their characteristics.