Institute for Transportation

About the research

Cape seals, which have been applied in several countries as well as the United States for many years, have never before been used by counties in the State of Iowa. As part of the Clinton County Pilot Demonstration Project of Cape Seals endorsed by the Iowa Highway Research Board (IHRB) serving as Iowa’s State Transportation Innovation Council (STIC), this study will (1) perform data collection and monitoring activities at the Cape Seal Pilot Demonstration Project site in Clinton County and (2) collect before and after stakeholder input to measure perceptions about the project and cape seal performance. This will be achieved through the execution of the following primary tasks: (1) documenting construction activities and executing a showcase/open house during project construction, (2) monitoring and evaluating pavement performance regarding the effectiveness of the innovations, (3) executing subsequent technology transfer and information dissemination activities and developing implementation plans with recommendations, and (4) publishing final research project documents. This research project would be highly helpful in scientifically documenting the performance of cape seal application over its service life and in providing the necessary data for the Iowa Department of Transportation (DOT) and Iowa counties who are considering deploying cape seals as standard pavement preservation practices (if the deployment is successful).

About the research

The objective of this research is to assess when each type of barrier should be used in two-lane two-way (TLTW) work zones and to develop guidelines for their use. This includes evaluation of the safety and operational impacts as well as an assessment of the tradeoffs in terms of benefit and cost.

About the research

The goal of this study is to complete a comprehensive evaluation of the flood reduction benefits of existing on-road structures (ORS). This work will be performed in five selected HUC12s in Iowa. To accomplish this objective the research team will use the process-based hydrologic model GHOST to run multi-year continuous simulations using both historic precipitation conditions as well as increased precipitation conditions that represent the projected changes in heavy precipitation by the mid-and late-21st century.

About the research

Holding strategies is an approach that began being considered and assessed by the Iowa Department of Transportation (DOT) in 2013. Assessment of several holding strategies was initiated with the construction of ten different test sections over 13.6 miles on Iowa Highway 93 between Sumner and Fayette. IA 93 is a lightly traveled two-lane rural highway with a flexible pavement system. The annual average daily traffic (AADT) on this road was 1040 with 3 percent heavy vehicles. A pavement condition survey conducted in July 2013 prior to construction indicated that the existing pavement was in poor condition with a pavement condition index (PCI) of 32. According to the ASTM designation, standard practice for roads and parking lots pavement condition index surveys, roads with PCI values less than 55 are considered to be in poor condition and require maintenance improvement to increase the drivability of the road. The predominant distress type of the existing pavement was top-down cracking. Severe raveling, potholes, and edge breaks were also observed during the pavement condition survey. The objective of this study is to evaluate holding strategy treatments that can be used to improve the serviceability and extend the service life of a deteriorated low-volume road.

About the research

Virtual reality (VR) technology can be a powerful platform for training Iowa Department of Transportation (DOT) officers for tasks such as Level VI inspections, walkarounds, and response-to-emergencies. Full-scale, 3D, highly interactive VR simulations allow for practicing inspection and response tasks. At the same time, the various interactions can be captured and stored to generate task response reports and to facilitate in-task After Action Reviews. The research framework is for three radiation inspections and/or emergency response simulations (or other simulations based on Iowa DOT needs).

About the research

Effective driver education should provide a solid foundation for novice drivers in order to establish good driving habits and be prepared for the variety of driving conditions present in Iowa. Accomplishing this requires a data-driven, scientific approach to understand the safety issues and challenges for novice drivers in order to develop a driver education curriculum that meets their needs. On the other hand, development and maintenance of an entire Driver Education program similar to what is currently available from vendors is a rather resource- and time-intensive undertaking. This research takes a balanced approach in addressing the core driver education needs in Iowa while leveraging existing resources. Specifically, the project will accomplish the following:

• Compare the current Iowa driver education curriculum against national/regional programs and standards and identify gaps
• Survey professional and parent driving instructors in Iowa to identify gaps and best practices
• Identify novice driver safety issues through a summary of available information and analyses of the Iowa crash data
• Identify gaps in the Iowa Driver Education curriculum using the information gathered in project activities
• Develop curriculum content for the most critical gaps
• Develop an outline of suggested content for a driving curriculum that meet the needs of novice drivers in Iowa
• Provide guidance for incorporation of the proposed curriculum and developed content use and incorporation by vendors and driving instructors
• Provide guidance to assist private vendors/instructors on updating teaching and delivery methods
• Develop guidelines for adoption of curriculums by private vendors for Iowa
• Develop recommendations on teaching and delivery methods
• Draft language to incorporate changes into the Iowa Code

About the research

Transverse cracks in concrete bridge decks sometimes initiate in the early stages of the bridge service life, usually just after construction. Cracks in the bridge deck can accelerate the deterioration of the deck concrete, provide a direct pathway for the intrusion of water and chlorides to the deck reinforcement, and detract from the aesthetics. This eventually results in increased maintenance costs and reduced bridge service life.

The goal of this research was to identify factors that consistently lead to the formation of early-age transverse cracks for mitigation in the future. To obtain a comprehensive evaluation and include as many factors as possible in the research, the primary research investigation was conducted in three stages with varying numbers of bridges and factors considered in each stage.

The first stage was carried out on 2,675 bridges constructed in Iowa between 1900 and 2020. The goal of this stage was to identify the correlation between deck cracking and six parameters: deck concrete type (high-performance concrete [HPC] or non-HPC), maximum span length, maximum structure length, Iowa Department of Transportation (DOT) District, year built, and main structure type.

The second stage was conducted to include additional bridge parameters—but with a smaller number of bridges. A group of 20 bridges was selected after reviewing inspection reports for 116 bridges constructed between 2013 and 2018. Various bridge parameters in three main categories, structural, construction, and material, were investigated.

The third stage was carried out based on data collected from six field visits while deck concrete was being placed. The parameters investigated in this stage included evaporation rate (lb/ft²/h), air temperature (°F), concrete temperature (°F), relative humidity (%), and wind speed (mph).

The results from the three investigation stages were compared with the research results documented in another Iowa DOT report. Based on the research findings from each stage of investigation, the various parameters were classified as having either direct correlation, no correlation, slight positive correlation, or slight negative correlation.

About the research

Although bridge fires are not frequent events, they pose impacts on safety, traffic flow, and the economy given bridge repairs or replacement can be costly. A lack of information and the tools needed to evaluate fire damage to concrete bridges and to aid in decisions for both immediate and long-term use of fire-damaged bridges was the impetus for this research.

On October 30, 2019, multiple items within a homeless encampment were set on fire beneath the I-29 northbound bridge over the Perry Creek conduit in Sioux City, Iowa. The fire was exacerbated when a propane tank became engulfed by the flames. The bridge girders and deck were particularly vulnerable to the ground fire because of the minimal ground clearance (about 6 ft) in comparison to that of most other bridges.

Despite this unfortunate incident, it provided an opportunity to learn more about the residual condition and strength of the bridge girders through a research study. The Iowa Department of Transportation (DOT) elected for the removal and replacement of the bridge, which allowed for girders to be removed and undergo testing.

Three fire-damaged girders were selected from the bridge, carefully removed, and transported to the Iowa DOT maintenance yard in Ames, Iowa. Each girder was visually assessed and selected based on the apparent level of damage incurred: one low-level, one mid-level, and one higher-level. The goal was to compare and contrast apparent levels of damage and assess the impacts each level of damage had on the serviceability and strength of the girder.

This project provides the results and recommendations resulting from the completed load testing. The results will assist in providing more technical information with respect to fire-damaged girders to help bridge owners to develop guidelines for assessment and repair.

About the research

The goal of this project was to assess the potential and develop protocols for the use of high-resolution light detection and ranging (LiDAR) and multispectral imagery to evaluate environmental characteristics of Iowa Department of Transportation (DOT) project areas, with particular attention to identifying federally protected wetland areas that would require mitigation if removed or significantly altered during a road construction project.

Specifically, the research team evaluated how LiDAR and multispectral imagery can support the assessment of design alternatives and whether the data could help DOT staff select alternatives earlier and with less required fieldwork.

During the investigation, which included four objectives, an automated ArcGIS Pro tool that leverages Python and ArcGIS routines to identify potential jurisdictional wetlands based on data derived from LiDAR digital elevation models was developed.

The procedure is a first-pass screening tool that will allow Iowa DOT wetland delineation staff to focus their attention on areas likely to be wetlands, rather than having to scrutinize an entire study area with the same level of attention. The underlying classification model currently over-identifies wetland areas, but much of the overidentification has to do with where exactly the boundaries are mapped.

The final toolboxes and routines required to run the wetland classifying procedures are packaged into shareable toolboxes and have been provided and demonstrated to Iowa DOT staff. Using the automated procedure is expected to save time in wetland delineation by allowing staff to prioritize high-probability areas for further study.

The appendix in the report contains the Wetland Classification Tool User Guide that was developed as part of this project.

About the research

Longitudinal joints are thought to provide relief from expansion and contraction of the bridge deck resulting from temperature change, shrinkage, and live loads. Historically, however, these joints have been known to leak, allowing chloride-laden water to reach the bottom of the deck overhang and even the exterior girders.

One of the primary conclusions from the previous Phase I project was that the development of cracking in bridge decks appears to be less dependent on the total width of the deck and more dependent on restraint of the abutment to temperature changes and, in particular, temperature gradients. Based on the results of that research, a 115 ft long, 228 ft wide, bridge in Black Hawk County, Iowa was selected and designed to incorporate a thermal isolation barrier.

The objective of this research was to follow and document the design, construction, and performance of the bridge in Black Hawk County with a specific focus on the success of the deck crack mitigation efforts. To achieve this objective, the newly constructed bridge on Viking Road over IA 58 was selected for this study.

A nearly two-year-long monitoring period enhanced by multiple bridge inspections was conducted. In addition, an analytical study was conducted to investigate the efficacy of the isolation barrier on resisting the cracking at the end of the deck for an integral abutment bridge.

The results confirmed the findings from the Phase I research that development of cracking in bridge decks seems less dependent on the total width of the deck. The finite element model results indicated the maximum deck strain to be 46% greater without the effects of the thermal isolation barrier. This indicated that, without the thermal isolation barrier, the Viking Road Bridge could see cracking at the end of its deck.

The researchers recommend the use of a thermal isolation barrier between the abutment and backfill soils for wide integral abutment bridges as one way to lengthen the service life of these bridge decks while reducing maintenance, rehabilitation, and/or replacement costs as well.