Safety Evaluation of Permissive Flashing Yellow Arrows for Left-Turn Movements in Missouri

With over a decade of crash data available since the beginning of flashing yellow arrow (FYA) use, MoDOT decided to objectively investigate the safety performance of the system. Additionally, they wished to have an accurate inventory of all FYA installations statewide, and a determination of the benefit-cost ratio of the signal system. A virtual survey of every signalized intersection on the MoDOT system revealed 841 FYA signals, and the research team either recorded dates relayed by MoDOT or estimated them from as-built plans or photo logs. A simple before and after analysis revealed FYA operation appears to reduce KABC left turn opposite direction crashes about 14 percent and left turn opposite direction O crashes approximately 18 percent when protected-permissive left turn phasing is used before and after FYA installation. Further, this analysis estimates that the lifecycle benefits of installing FYA on an intersection approach are expected to be approximately 5 to 44 times greater than the installation cost, depending on the left turn phasing used before and after FYA installation.

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Report number: cmr 23-005
Published: February 2023

Project number: TR202102
Authors: Joseph G. Jones, Nick Foster, and Kush Bhagat

Performing organization: Leidos, Inc.

Development of a Geotechnical Asset Management Collection and Rating Program for Missouri Department of Transportation

The Missouri DOT research team, led by Landslide Technology, developed a prototype Geotechnical Asset Management (GAM) program through close collaboration with MoDOT geotechnical engineers and MoDOT’s IT group.  The team adjusted published and commonly accepted categories from state and federal GAM inventory and rating approaches to match conditions specific to Missouri. The GAM program compiles condition and risk assessment for six asset types: engineered embankments, retaining walls, rock slopes, soil slopes, subsidence, and subgrade. Subsidence and subgrade improvements were successfully incorporated into Missouri’s GAM program despite not being previously incorporated into an other DOT’s GAM inventory. The risk assessment rating developed for this project allows DOTs to approximate risk in the absence of site-specific maintenance or accident records.  Data is collected via ESRI’s Survey123 Application before being scraped and processed in MoDOT’s TMS system, where it is added to other department datasets. The application was field-tested on National Highway System (NHS) routes in the Northwest and Northeast Districts in October 2022.

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Report number: cmr 23-004
Published: February 2023

Project number: TR202007
Authors: Aine E. Mines, Darren L. Beckstrand, and Michael D. Bunn 

Performing organization: Landslide Technology, Inc.

Fiber Reinforced Concrete for Bridge Deck Overlays

This report reviews available research literature and reports on Fiber Reinforced Concrete (FRC) mixtures to recognize best practices of using FRC overlay mixtures and identify products with the potential of being successfully utilized in Missouri. State DOT representatives were surveyed to consolidate the current state of practice as it relates to the use of FRC, particularly for bridge decks. The survey shows that there are a variety of approaches and implementation methods from coast to coast. Also reported are the findings of a laboratory program involving evaluation of twelve fibers, representing a broad spectrum of available fiber types. Each fiber was intermixed into a representative concrete mixture at three different dosages to evaluate the performance of the recommended range. Testing was carried out for standard physical strength metrics, durability performance, and specialized FRC toughness. Additionally, the impact of fibers on restrained shrinkage cracking and tensile bond strength of FRC was evaluated. Results indicated that fibers can be introduced to concrete mixtures to obtain workable mixtures with little change to the underlying concrete mixture proportions. A generalized trend could not be established between fiber characteristics and mechanical or durability properties. Good correlation was observed between flexural toughness and fiber dosage. A noticeable difference was documented between the performance of synthetic and steel fibers when subjected to the ASTM C1609 test. The ASTM C1550 test indicated varying behaviors at different prescribed deflection levels. Restrained shrinkage testing showed the lower dosages recommended showed little improvement over the non-FRC control mixture; higher fiber dosages showed improvements in resistance to restrained shrinkage cracking. Many concerns regarding the inclusion of fibers in concrete were overcome and, if eliminated, FRC can result in mixtures with similar strength and durability characteristics to traditional non-FRC concrete with improved crack resistance. These are ideal characteristics of an overlay concrete that needs to be compliant with the underlying concrete while not reflecting through any existing cracks to prolong the life of the underlying structural concrete. 

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Report number: cmr 23-003
Published: February 2023

Project number: TR202113
Authors: Kamran Amini, Pavan Vaddey, Benjamin F. Birch, and David Corr 

Performing organization: Construction Technology Laboratories, Inc. (CTLGroup)

Landslide Monitoring Methods: Application of Existing Technologies to Long-Term and Real-Time Monitoring of Slope Movements

Various landslide monitoring techniques were applied concurrently to a known cut-slope landslide and a previously unknown fill slope failure, both on the Ozark Mountain Highroad (Missouri Route 76) near Branson, Missouri. Both subsurface and drone-based monitoring techniques were employed so that the strengths and weaknesses of the various monitoring techniques could be compared. Slope inclinometer casings and vibrating wire piezometers were installed at the three borings drilled in the project area. An in-place inclinometer was installed in one boring to demonstrate the effectiveness of instrumented landslide monitoring. Dataloggers were connected to a cellular modem to enable real-time monitoring of the instruments through a web-based interface. LiDAR data was collected by drone annually.  The research team developed a subsurface geometry for both slides and identified movement triggering events.  The team also compared the various monitoring techniques to provide guidance for future selection of long-term monitoring methods at other unstable slopes.

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Report number: cmr 23-002
Published: February 2023

Project number: TR202016
Authors: Aine E. Mines, Darren L. Beckstrand, and Michael D. Bunn

Performing organization: Landslide Technology, Inc.