Institute for Transportation

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

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

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.

About the research

Collection of project level work zone performance measures (i.e., queue length, travel speed) in the field is difficult because setting up data collection equipment within the work zone can be disruptive and the lack of right-of-way can force data collectors to be situated in unsafe locations. In addition, the most recent emission model, the Environmental Protection Agency’s Motor Vehicle Emission Simulator (MOVES) requires second-by-second vehicle activity, which may require methods such as instrumented vehicles. Consequently, data needs for both types of analyses are resource-intensive.

The objective of this research is to demonstrate the utility of linking micro-simulation output with work zone and emission models. The project will collect data for several work zone and operational scenarios and develop models with the micro-simulation model, ViSSIM. Work zone model scenario output (i.e., queue length, travel speed) will be compared to field data and drawbacks in use for analysis of work zone performance measures identified. The utility of using micro-simulation model output for work zone analysis will be documented.

ViSSIM output from operational scenarios (speed/acceleration) will be compared to field data to assess the accuracy of micro-simulation models in providing realistic estimates of vehicle activity as input to MOVES. Results will be summarized to demonstrate the applicability of linking micro-simulated vehicle activity data with emissions models to better estimate the emission impacts of different transportation strategies.

The team will also work with researchers at the University of Iowa (UI) to take the analysis one step further and integrate micro-simulation model output with driving simulators. (UI is preparing a separate proposal for their portion of the work.) Completion of most project objectives for this research, however, can be completed independently if the UI proposal is not funded.

The requested Mid-America Transportation Center (MATC) funds will be matched to a project funded by the Smart Work Zone Deployment Initiative (SWZDI) titled Work Zone Safety Performance Measures.

About the research

The vast majority of asphalt materials used in highway construction are derived currently from the distillation of crude petroleum. The increasing demand for products derived from crude petroleum, coupled with constrained supply, has led to substantial price increases in crude petroleum products including asphalt. To further meet the increased demand for transportation fuels, many refineries have installed coking facilities that remove asphalt from the marketplace, further impacting the pricing of asphalt.

The evolution of the biorefineries producing transportation fuels, specialty chemical products, and food products has created opportunities for using derived co-products in the asphalt industry. These co-products may be used to replace crude petroleum-derived asphalt, either partially or fully, or be used as beneficial additives for mitigating moisture damage, as an example.

Assessment and characterization of these materials, including chemical compatibility, rheological testing, and formulation for use in asphalt paving, is needed. This project is a collaborative one combining Kansas State University’s expertise in analytical chemistry and asphalt mixture characterization with Iowa State University’s expertise in using bio-based materials in asphalt materials and rheological characterization.

This project addresses the U.S. Department of Transportation’s strategic goals associated with state of good repair, sustainability, and economic competitiveness.

About the research

Highway agencies spend millions of dollars to ensure safe and efficient winter travel. However, the effectiveness of winter-weather maintenance practices on safety and mobility are somewhat difficult to quantify. Safety and Mobility Impacts of Winter Weather – Phase 1 investigated opportunities for improving traffic safety on state-maintained roads in Iowa during winter-weather conditions. In Phase 2, three Iowa Department of Transportation (DOT) high-priority sites were evaluated and realistic maintenance and operations mitigation strategies were also identified.

In this project, site prioritization techniques for identifying roadway segments with the potential for safety improvements related to winter-weather crashes, were developed through traditional naïve statistical methods by using raw crash data for seven winter seasons and previously developed metrics. Additionally, crash frequency models were developed using integrated crash data for four winter seasons, with the objective of identifying factors that affect crash frequency during winter seasons and screening roadway segments using the empirical Bayes technique.

Based on these prioritization techniques, 11 sites were identified and analyzed in conjunction with input from Iowa DOT district maintenance managers and snowplow operators and the Iowa DOT Road Weather Information System (RWIS) coordinator.