Institute for Transportation

About the research

Internal curing is the practice of providing small, well-distributed reservoirs of water throughout a concrete section such that the w/cm of the mixture can be kept low, but the water can later be delivered to hydrating cement as the system dries out. Internal curing has been reported to be effective in reducing shrinkage cracking, improving potential durability of concrete mixtures, and most notably, reducing warping and associated cracking in pavements and slabs on grade.

Currently, the use of light-weight fine aggregate (LWFA) is the most common practice in the US to produce internally cured concrete. This method, however, necessitates pre-saturation of aggregate at concrete batch plants in accordance with a set timeline. This may increase costs related to stockpile management in addition to the costs and emissions associated with production and hauling the LWFA.

The use of superabsorbent polymers (SAP) as a means of internal curing can address such problems, while still promoting hydration and reducing the risk of early age cracking. However, there has been relatively little work conducted in the US on these materials. The aim of the work is to conduct laboratory work to address some remaining questions:

• How should SAP products be specified?
• How much is needed?
• Can SAPs be dry batched with additional water in the mixture without compromising performance?
• How are mixtures affected by their use?

About the research

The Iowa Highway Research Board funded a study (IHRB Project TR-761) to determine the feasibility of an Iowa Public Works Service Bureau. As a part of that study, a questionnaire was emailed to representatives of all cities with a population exceeding 250 people to determine if there was interest in developing a public works service bureau. The questions dealt with a city’s interest in web applications including elements such as a database of city contacts, asset management, organizational charts, job descriptions, pay levels, sample ordinances, sample policies, and communications with the Iowa Department of Transportation (DOT). Over 80% of the respondents indicated that they were highly or somewhat likely to use those applications.

With that indication of interest, potential organizational structures and funding were evaluated. Based on those evaluations, a majority of the Technical Advisory Committee recommended pursuing a project to establish the Iowa Public Works Service Bureau within the Statewide Urban Design and Specifications program with permanent funding from the street construction portion of Iowa’s Road Use Tax Fund. Due to the time required to work with the Governor’s office and the legislature to establish the permanent funding, a two-year Phase 2 project was recommended with funding from the IHRB. This project will involve creating the website elements, hiring two programmers to establish the applications, establishing a permanent advisory committee, and working to establish permanent funding with a Road Use Tax off-the-top allocation.

About the research

A life-cycle cost analysis (LCCA) tool for bridges was successfully developed as part of the Phase I project and takes into consideration the deterioration rates specific to Iowa bridge decks at two-year time intervals and aims to predict the agency and user costs associated with preserving, rehabilitating, and repairing the bridge decks. This offers a unique advantage over Iowa’s current system, which selects projects based on the lowest bid or estimated initial cost. In addition, the developed tool is extendable to cover various bridge elements, if needed. However, the initial tool did not take into consideration various sources of uncertainty or include an optional choice to consider indirect costs in the calculations. In addition, feedback from potential users of the tool will be necessary to further enhance the tool.

Phase II seeks to enhance the usability of the tool. Specifically, this tool will deliver firsthand information about how the timing, frequency, and procedure used for the maintenance of a set of similar bridges can lead to different service life extensions and future needs. This can be immediately employed to identify the most promising maintenance and management strategies for the bridges in service.

About the research

Following too closely (tailgating) is a persistent problem throughout the roadway system, and its consequences can be particularly severe in work zones. In fact, rear-end collisions are the most common type of crash in work zones. Maintaining sufficient car-following gaps allows drivers enough time to react to unexpected and complex situations at work zones, and thus can reduce the rear-end collision potential. Work zones provide an opportunity to deliver messaging aimed at encouraging safer driving behavior at moments when that information is highly relevant.

This project will evaluate the effectiveness of roadside messaging techniques on increasing vehicle spacing (headway) in work zones.Through a review of the state-of-the-art and the state-of-the-practice, measures and techniques for encouraging drivers to maintain proper spacing will be summarized. Messaging techniques that encourage safe following distances in work zones will be developed and the effectiveness of these messages will be evaluated using vehicle speed and car-following (headway) data collected from sensors deployed at work zones.

About the research

This project reviewed various stakeholders’ current needs for pre-construction, real-time, and post-construction work zone information and compared these needs to the available work zone data sources and standards. The analysis identified a substantial mismatch between the roadway and lane closure data currently available and the data required to manage work zone traffic impacts effectively. To address this gap, the project developed a conceptual prototype for a tool that would facilitate self-reporting of closure details by contractors and maintenance crews.

About the research

This study investigated the differences between the American Railway Engineering and Maintenance-of-Way Association (AREMA), American Association of State Highway and Transportation Officials (AASHTO), and Iowa Department of Transportation (DOT) concerning vehicular collisions. The researchers evaluated the performance of common Iowa bridges and their components when an 80 kip tractor-semitrailer collides into them. The researchers also performed a parametric study on a frame pier and T-pier that experience vehicular collision.

The frame pier with two 3.5 ft column diameters with a spiral of #5 rebar and 4 in. pitch experiences minor damage when impacted by a tractor-semitrailer at an impact velocity of 50 mph. There is, however, severe damage and failure for the impact velocity of 70 mph and 90 mph, respectively. The T-pier commonly used in Iowa does not collapse under any of the three impact velocities. The minimum requirements for a crash wall specified by the Iowa DOT were able to keep the frame pier from failure when it was struck by a tractor-semitrailer traveling at each of the three impact velocities. The Iowa DOT’s 54 in. tall concrete barrier successfully redirects a tractor-semitrailer and therefore prevents it from hitting the frame pier it is set up to protect.

The frame pier with two column diameters of 4 ft with at least 1.0% longitudinal reinforcement, #5 spiral rebar at a 4 in. pitch, and Grade 60 steel, did not collapse under any of the three impact velocities. The T-pier with no ties experiences minor damage when impacted at the 50 mph impact velocity. However, ties spaced at 24 in. and 12 in. are required for minor damage at a 70 mph and 90 mph impact velocity, respectively.

The damage ratio index (DRI) values and damage description for the frame pier accurately predicted the damage observed in the frame pier due to vehicular collision. The DRI damage state description for the frame pier did not accurately describe the damage for the T-pier. Therefore, a DRI damage state description table was developed for the T-pier.

About the research

Traffic signs provide warning and guidance information to drivers 24 hours a day. These signs also represent a significant maintenance and replacement concern and cost for agencies with the advent of retroreflectivity requirements. In some cases, agencies choose to replace their signs in conjunction with the end of the manufacturer warranty period or other time intervals to ensure that signs maintain their retroreflectivity. However, this could result in signs being replaced while they still exceed their minimum retroreflectivity requirements with labor and material costs being incurred years before necessary.

The research team evaluated retroreflectivity data from in-service signs in Iowa to determine expected sign life values for agencies. The researchers acquired sign retroreflectivity data from two Iowa counties and one city for analysis. The team utilized 10,799 retroreflectivity data points across three different sheeting materials for a variety of sign types. The researchers used linear regression to evaluate the two components of greatest interest to the research: the age of a sign versus its respective retroreflectivity value.

The researchers developed 65 linear regression models to evaluate signs by sheeting type and Federal Highway Administration (FHWA) Manual on Uniform Traffic Control Devices (MUTCD) category (regulatory and warning), as well as sign orientation (north, south, east, and west).

The results of the analysis indicated that all sheeting materials, sign types, and sign directions were predicted to have lives of at least 10 years before falling below MUTCD minimums. Plots of sign retroreflectivity versus sign age indicated that many retroreflectivity readings still remained well above the MUTCD minimums at the predicted age where failure was expected. In general, the predicted lives for a material/sign type/direction combination were greater than five years longer than the manufacturer warranty periods. For conservative purposes, agencies could consider a sign to be approaching the MUTCD minimum retroreflectivity level at approximately five years past the manufacturer warranty based on the results of this research.

About the research

The Iowa Automated Permitting System (IAPS) is an online oversize/overweight/over dimension permitting system for the motor carrier industry based on the Bentley SuperLoad® product. IAPS began production operations in December 2013. As of 2017, among the 100,000 permits issued by the Iowa Department of Transportation (DOT) annually, about half of them were issued automatically. In May 2019, Governor Reynolds signed Senate File 629, an Act relating to permits for vehicles of excessive size and weight, including vehicles transporting raw forest products, and providing for fees. The Iowa Legislature requested that the Iowa DOT report on the IAPS to allow electronic processing of oversize/overweight (OS/OW) permits for non-primary roads.This includes the application, review, routing, approval, and payment(s) to the appropriate jurisdiction(s).

The Institute for Transportation at Iowa State University is tasked with preparing the report to legislature regarding implementation options of performing OS/OW permitting for local public authorities (LPA) in IAPS. The objectives of this project include:

• Review the current IAPS system capabilities
• Develop implementation options for consideration by the Iowa DOT
• Identify the barriers, possible solutions, and required resources to implement the options proposed

About the research

The Iowa Department of Transportation has received funding for an Accelerated Innovation Deployment (AID) project from the Federal Highway Administration to construct bridges using box beams made with ultra-high performance concrete (UHPC). Through the use of this approach to accelerated bridge construction (ABC), the duration of off-site detours during the course of a project will be reduced. The reduced construction timeline is expected to translate into improved safety for the traveling public, as the shortened duration of off-site detour routes would reduce exposure and the potential for crashes to occur along those routes.

About the research

This project is part of the main Iowa Department of Transportation-sponsored project, “Iowa DOT Operations Division Cooperative Autonomous Transportation (CAT) Research Support.”

This project provides funding for CTRE support to the Iowa DOT Operations Division specific to Cooperative Automated Transportation (CAT) research, applications, data analytics, demonstrations, and discovery. This work is focused to support Iowa DOTs vision of delivering a safe, reliable, and efficient transportation system by developing a supportive digitally connected driving environment.

The objective of this task is to seek out if there are existing products on the market, or products that could be modified, to automate the alerting system.

The Iowa DOT currently uses an audible warning system with their attenuator setup. However, the system must be activated manually by the attenuator driver looking in their rear-view mirror. This is a two-stage process where lights are flashed first and if the vehicle continues to approach the truck, nor change lanes, a very loud beeping sound is broadcasted.

To date, CTRE has completed a literature review of similar systems and held numerous conversations with industry. This includes sharing DOT needs and existing equipment capabilities (power, mounting, electrical, etc.) with a number of companies of which at least two were considering building or modifying a suitable device.

Depending on industry response and DOT direction, FY21 efforts could include purchase of several units for evaluation in terms of function, practicality, and costs. The DOT staff lead is Donna Matulac with support from John Hart.