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Office of Safety and Office of Infrastructure Project Results

Geosynthetic Reinforced Soil-Integrated Bridge System

Evaluation Overview

The evaluation team examined the Federal Highway Administration's (FHWA’s) research and development process for the Geosynthetic Reinforced Soil-Integrated Bridge System (GRS-IBS) program. GRS technology consists of closely spaced layers of geosynthetic reinforcement and compacted granular fill material. FHWA has worked to evolve the technology into GRS-IBS, which blends the roadway into the superstructure.

The evaluation focused on early research development, deployment decisions, barriers to GRS-IBS deployment, and whether GRS-IBS is a disruptive technology.

Evaluation Results

The evaluation found that:

  • FHWA pursued GRS-IBS research because it showed potential for saving time and money in the design and construction of single-span bridges.
  • FHWA activities increased awareness of GRS-IBS among potential builders and bridge owners.
  • FHWA activities and outreach improved the attitude of potential users toward GRS-IBS.
  • Stakeholders mentioned multiple benefits from GRS-IBS, including cost savings, ease of construction, and time savings.

Recommendations

A key recommendation was to make market research part of engineering research. Market research can help guide the selection of research topics, and improve the likelihood of implementing new technologies by identifying potential problems that might be encountered by technology users and—importantly—developing solutions prior to adoption.

Gusset Plates

Evaluation Overview

The evaluation team examined FHWA’s Gusset Plate Project to better understand how FHWA’s investment in gusset plate research has affected the design and rating of gusset plates.

On August 1, 2007, I–35W Mississippi River Bridge in Minneapolis, MN, collapsed. The National Transportation Safety Board (NTSB) turned to FHWA to provide technical expertise during their investigation, and the NTSB then issued recommendations to FHWA to prevent similar catastrophic bridge failures. The Gusset Plate Project was an FHWA research project to assess the performance and design of steel gusset plate connections.

Evaluation Results

The evaluation found that:

  • FHWA provided vital support to NTSB to determine the cause of the I–35W Bridge collapse.
  • FHWA’s work helped inform updates to the American Association of State Transportation Officials’ specifications.
  • FHWA’s active and ongoing engagement of transportation stakeholders expedited delivery of new information regarding the design and load rating of gusset plates.

Recommendations

The evaluation recommended that FHWA should remain flexible on how its research funding is used. In this particular case, given the scale of the emergency and the immediate need for research and information, funds were redirected into the Gusset Plate Project. FHWA management was flexible with funding, and legislation at the time was also flexible enough to provide this accommodation.

Precast Concrete Pavement

Evaluation Overview

The evaluation team examined the outcomes and impacts of FHWA research and educational outreach related to precast concrete pavement technology. Precast concrete pavement (PCP) refers to high-quality, durable, prefabricated concrete panels used to repair roads during offpeak travel times. PCP panels are quick to install, and road maintenance professionals can use them for a range of projects in high-traffic areas.

Evaluation Results

Some of the main findings of the evaluation included:

  • FHWA activities provided guidance to States interested in deploying PCP and furthered the development and number of PCP installations.
  • PCP generates travel-time savings by reducing road-closure times and avoiding significant detours in areas that are difficult to repair (bridge approaches, shoulders, and ramps).
  • PCP allows for overnight installation and is faster to install than traditional concrete.
  • PCP is more durable and requires less maintenance and fewer repairs compared to cast-in-place and high-early-strength concrete.

Recommendations

One recommendation was that FHWA should continue to support PCP and document institutional knowledge without endorsing particular systems. An additional recommendation was that States should conduct trial installations prior to beginning construction. This has been shown to lower costs from unforeseen complications, increasing the overall return on investment for PCP usage.

Roundabouts

Evaluation Overview

The evaluation team assessed the effects of FHWA’s investment in roundabout research on the availability and quality of such research, the adoption of roundabouts in the United States, and the impacts of those roundabouts on safety, operational, and environmental performance of the United States transportation system. A roundabout is a circular intersection in which approaching traffic yields to circulating traffic. In the United States, roundabouts are often confused with traffic circles and rotaries.

Evaluation Results

Some of the main findings of the evaluation included:

  • FHWA roundabout research increased awareness and changed attitudes in the transportation community toward the roundabout as a safety countermeasure.
  • FHWA accelerated early adoption and contributed to an increase in the number of roundabouts built in the United States.
  • The literature demonstrates significant safety benefits of roundabouts, as well as operational, environmental, and lifecycle cost impacts of roundabouts.

Recommendations

A key recommendation was to research and promote information on roundabout costs and strategies for reducing roundabout costs. Initial roundabout capital costs appear to be a barrier to roundabout adoption, so additional research should be undertaken to identify the underlying cause for the high costs, in which the potential for cost savings may exist without compromising safety and performance benefits.

Completed reports can be viewed at https://www.fhwa.dot.gov/publications/research/general/18042/index.cfm.

Updated: Monday, December 2, 2019