Institute for Transportation

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.

About the research

In 2010, 16.5 percent of all fatal vehicle crashes in Iowa involved large trucks compared to the national average of 7.8 percent. Only about 16 percent of these fatalities involved the occupants of the heavy vehicles, meaning that a majority of the fatalities in fatal crashes involve non-heavy truck occupants. These statistics demonstrate the severe nature of heavy truck crashes and underscore the serious impact that these crashes can have on the traveling public. These statistics also indicate Iowa may have a disproportionately higher safety risk compared to the nation with respect to heavy truck safety.

Several national studies, and a few statewide studies have investigated large truck crashes; however, no rigorous analysis of heavy truck crashes has been conducted for Iowa. The objective of this study was to investigate and identify the causes, locations, and other factors related to heavy truck crashes in Iowa with the goal of reducing crashes and promoting safety. To achieve this objective, this study used the most current statewide data of heavy truck crashes in Iowa.

This study also attempted to assess crash experience with respect to length of commercial driver’s license (CDL) licensure using the most recent five years of CDL data linked to the before mentioned crash data. In addition, this study used inspection and citation data from the Iowa Department of Transportation (DOT) Motor Vehicle Division and Iowa State Patrol to investigate the relationship between enforcement activities and crash experience.

About the research

Assessing the structural integrity of bridge foundations is critical to ensuring the safety of the traveling public. However, nondestructive methods currently used in practice to determine the quality of drilled shaft foundations are severely limited by their inability to provide full coverage of the foundation cross-section, particularly in the critically-important region outside of the rebar cage.

The goal of this project is to evaluate the accuracy of a new thermal integrity profiling (TIP) technique for quality assurance of deep foundations. The TIP method utilizes infrared thermal probes lowered into access pipes, which are cast into the foundation to measure the heat of hydration of curing concrete. Previous studies demonstrated that the technique can detect loss of concrete cover outside the rebar cage, as well as internal flaws such as cracking or voids. However, the studies did not assess the accuracy of the technique for indicating the specific location and extent of flaws.

This research project is a collaborative effort between the Institute for Transportation (InTrans) at Iowa State University and the Iowa Department of Transportation (DOT) to evaluate the accuracy of the TIP method. A full-scale test shaft will be constructed with voids at predetermined locations. Measurements of shaft integrity will be compared for the new TIP method and the cross-hole sonic logging (CSL) method, which is currently the most commonly used quality assurance tool for drilled shafts.

The ability and accuracy of the two techniques to detect the specific locations, size, and general shape of the known shaft defects will then be assessed. It is anticipated that the thermal integrity profiling will provide cost savings to the Iowa DOT as a more economical alternative to CSL testing, or as a screening tool to identify which shafts should be further analyzed by CSL specialists.

About the research

As traffic-related work zone crashes continue to increase across the nation, safety of road users and workers has become a top priority for transportation agencies. Since inattention and irresponsible behavior by drivers are surmised to contribute to the frequency of work zone crashes, a program featuring extraordinary presence of and enforcement by law officers has been implemented in many states to address this concern. A literature search of such programs and related research was conducted. While the overall benefits of these activities have been found positive, much of the evidence has been anecdotal. To assess the scope of extra work zone enforcement programs, a survey was developed and distributed to state departments of transportation across the nation. This survey sought information regarding these efforts such as criteria for selection of target work zones, methods of enforcement operations, and beneficial results. A special survey was also designed and distributed to enforcement agencies in Iowa and other selected states. In addition to the surveys, personal contacts and office visits were conducted by the research team staff.

The study found that use of extra enforcement in work zones is a common practice in many states and these activities appear to be increasing. Current literature, survey responses, and interviews have all indicated a prevalent opinion for the benefits of increased law enforcement presence and activity in work zones. Very few comments offered conclusions of negative impacts, such as additional congestion, from these efforts. However, the beneficial effects of focused enforcement have not been intensively quantified. In addition, procedures for the use of law officers in work zones are quite inconsistent across the nation, as is the general implementation of specific legislation addressing work zone traffic violations. Similar variation can be found in funding levels and sources for enforcement activities in work zones among the states. Training of law officers prior to work zone duty does not appear to be commonly required, though the value of focused training is being recognized in some states.

As crashes and deaths continue to rise annually in our nation?s work zones, it is imperative that demonstrated beneficial programs such as the expanded use of law officers in these locations be continued, refined, and expanded. Future study is needed to supplement the knowledge base and provide guidance to agencies when considering the use of law enforcement to calm traffic, ensure compliance with traffic laws, and thus provide for safer work zones.

About the research

To support the analysis of driver behavior at rural freeway work zone lane closure merge points, CTRE staff collected traffic data at merge areas using video image processing technologies. The collection of data and the calculation of the capacity of lane closures are reported in a companion report, Traffic Management Strategies for Merge Areas in Rural Work Zones. These data are used in the work reported in this document and are used to calibrate a microscopic simulation model of a typical Iowa rural freeway lane closure.

About the research

Applying better management practices requires knowledge of the traffic flow properties and driver behavior in and around work zones, and knowledge of possible management strategies. The project reported here and in a companion report documents research that seeks to better understand traffic flow behavior at rural Interstate highway work zones and to estimate the traffic carrying capacity of work zone lane closures.

About the research

None available for this project

About the research

This project identified the benefits of distance sharing, needs for improved distance sharing capabilities among major transportation stakeholders in the region, and recommendations for meeting these needs under use, cost, and performance expectations identified by the stakeholders.