CLOSE OVERLAY
Project Details
STATUS

Completed

START DATE

06/04/21

END DATE

06/16/23

FOCUS AREAS

Infrastructure

RESEARCH CENTERS InTrans, CTRE, Iowa LTAP
SPONSORS

Minnesota Department of Transportation

Researchers
Principal Investigator
David Veneziano

Safety Circuit Rider, LTAP

Co-Principal Investigator
John Shaw
Co-Principal Investigator
Jonathan Wood

Faculty Affiliate, CTRE

About the research

While pedestrian safety countermeasures contribute to reducing vehicle-pedestrian crashes, their impacts on winter maintenance operations are sometimes overlooked during design. There is a need to investigate the best practice guidance and solutions for the design, installation and maintenance of pedestrian safety features for year-round maintenance. To address this, we conducted a search of literature as well as agency interviews to identify and document current best practices for designing and implementing pedestrian safety countermeasures for year-round maintainability. The countermeasures reviewed included curb ramps, crosswalk markings, corner radii, curb extensions, refuge islands, and speed humps and raised crosswalks. The information collected allowed for the development of conclusions and recommendations for these features. The design dimensions and features of pedestrian curb ramps are established by the Americans with Disabilities Act and should have a slope of greater than 1:12 and a maximum cross slope of 1:50. Durable materials can be used for crosswalk markings, and these can be grooved into the pavement to provide protection from abrasion. Bulb-outs should use a 1:2 or 1:3 upstream taper and a 1:3 downstream taper. When used, tight radii of 15 feet or less should be employed. Refuge islands can range from 6 feet or greater in width, 24 feet to 40 feet in length, with a 4-foot or greater walkway width. Finally speed humps and tables should be between 3-4 inches in height, with lengths of 12-14 feet (humps concave in shape) and up to 22 feet (tables).

Project Details
STATUS

Completed

START DATE

08/21/20

END DATE

10/10/23

FOCUS AREAS

Infrastructure

RESEARCH CENTERS InTrans, AMPP
SPONSORS

Minnesota Department of Transportation

Researchers
Principal Investigator
Chris Williams

Director, AMPP

Co-Principal Investigator
Eric Cochran

Faculty Affiliate

About the research

Asphalt pavements deteriorate from temperature cycling, moisture, oxidation, and loading-related distresses. Pavement preservation is critical in maintaining the functional and structural integrity of roads and extending pavement life. Surface treatments can prevent or restore the aging effects by rejuvenating and/or sealing the pavement’s surface, limiting further damage, and restoring its flexibility. This collaborative study of MnDOT, the National Road Research Alliance (NRRA), and Iowa State University investigates the efficacy of fog seal/bio-fog seal topical treatments based on soy-derived rejuvenators, epoxidized soybean oil (SESO), and BioMAG, which contains SESO and the biopolymer poly(acrylated epoxidized high oleic soybean oil) (PAEHOSO). Each topical treatment was applied at three locations in different asphalt binder grades to provide a comprehensive approach to their impacts on the dry time, reflectivity, friction, and permeability of the pavement course. It was observed that the bio-fog seal treatments improve the skid resistance of the pavement, do not affect the reflectivity of pavement markings, and are able to restore the stiffness of the asphalt mixtures. Additionally, the fog seals show fast setting and curing and allows the road to be open to traffic in less than 30 minutes.

Project Details
STATUS

Completed

START DATE

12/30/20

END DATE

08/31/21

FOCUS AREAS

Safety

RESEARCH CENTERS InTrans, CTRE
SPONSORS

Minnesota Department of Transportation

Researchers
Principal Investigator
Shauna Hallmark

Director, InTrans

Co-Principal Investigator
Neal Hawkins

Director Research Administration, ISU

About the research

Reduced traffic volumes resulting from COVID-19, along with the strain on enforcement during the pandemic, are thought to have produced higher speeds and more aggressive driving. Understanding the magnitude of speeding and other driver behaviors requires measurement and contrast. This project quantifies reductions in volume and the resulting differences in travel speeds across Minnesota along regular roads and within two work zones prior to and during the novel COVID-19 pandemic. The work includes a review of total crashes as well as fatal and serious injury crashes and includes a survey of law enforcement opinions. Findings based on 125 Automatic Traffic Recorders (ATR) and traffic Sensors quantify volume reductions, which, of course, were lower in 2020 but which varied considerably by location and month. Average speeds overall along with both the number and percentage of vehicles traveling greater than 15 mph over the posted speed limit increased in 2020. This information supports benchmarking and agency decision making.

Project Details
STATUS

Completed

START DATE

07/01/19

END DATE

09/30/22

FOCUS AREAS

Infrastructure

RESEARCH CENTERS InTrans, BEC
SPONSORS

Minnesota Department of Transportation

Researchers
Principal Investigator
Behrouz Shafei

Structural Engineer, BEC

Co-Principal Investigator
Brent Phares

Bridge Research Engineer, BEC

About the research

The strength and durability of reinforced concrete (RC) bridges are adversely affected by the deterioration of their structural members. When investigating bridges in need of maintenance and repair, the deterioration due to the corrosion of steel rebars is commonly found to be a primary source of structural damage and degradation. To ensure the safety and performance of RC bridges while reducing their direct and indirect costs, an accurate estimate of the extent of reinforcement section loss has central importance for a wide spectrum of engineers and decision-making authorities.

This research project investigated the steps required to achieve such rebar section loss estimates. To achieve this purpose, field assessments of rebar section loss were correlated with available predictive models and later calibrated to condition-specific field data. The outcome, which has been delivered in the form of steel reinforcement section loss guidance tables, directly contributes to understanding variability in rebar section loss when making loss predictions for use in structural evaluation. This facilitates planning preventive and/or corrective actions tailored to the condition state of deteriorating bridge elements.

Project Details
STATUS

Completed

START DATE

07/01/16

END DATE

08/31/18

FOCUS AREAS

Infrastructure

RESEARCH CENTERS InTrans, BEC
SPONSORS

Minnesota Department of Transportation

Researchers
Principal Investigator
An Chen
Co-Principal Investigator
Behrouz Shafei

Structural Engineer, BEC

About the research

Many state Departments of Transportation (DOT) across the US, including MnDOT, are experiencing problems associated with loose anchor bolts used in support structures (e.g., overhead signs, high-mast light tower (HMLT), and tall traffic signals). Specifically, MnDOT inspection crews have found loose nuts at most anchor bolt locations, even at some newly installed signs. Many of these nuts became loose in less than two years, even after being tightened by the maintenance crew following current recommended procedures. This situation has placed great strain on the resources from the districts’ maintenance group and also causes concerns related to inspection frequency and public safety. This project investigated causes of the loose anchor bolts and proposes solutions based on site surveying, field monitoring, laboratory study, and numerical analysis. The research team found that the tightening process proposed in AASHTO’s specification is a sufficient alternative for MnDOT, though it requires modification in three key areas: defining snug-tight, accounting for grip length, and recommending verification procedures. The research team quantified snug-tight values, and defined the relationship between torque, tension, and nut rotation through empirical constants. Recommendations are made for a new specification for MnDOT structures.

Project Details
STATUS

Completed

START DATE

10/16/20

END DATE

07/31/22

FOCUS AREAS

Infrastructure

RESEARCH CENTERS InTrans, PROSPER
SPONSORS

Minnesota Department of Transportation

Researchers
Principal Investigator
Halil Ceylan

Director, PROSPER

Co-Principal Investigator
Sunghwan Kim

Associate Director, PROSPER

Co-Principal Investigator
In-Ho Cho
Co-Principal Investigator
Eugene S. Takle
Co-Principal Investigator
Daniel Rajewski

About the research

An increase in freeze-thaw events will result in detrimental impacts on pavement systems. However, the impacts of recent climate changes on freeze-thaw cycles have not been well studied, although they are of interest to a broad number of transportation agencies. In this study, the number of freeze-thaw events at typical air temperature sensor level (e.g., 6 feet above the earth’s surface) as well as at different pavement layers and critical sub-pavement locations such as saturated subgrade within the active zone were quantified.

In response to global warming, current work resulted in rigorously quantified freeze-thaw events rooted in climate data from 1941 to 2020. Results indicated that in the recent 40 years (i.e., 1981–2020), Minnesota winters have become warmer by 1–2ºF daytime and 2–5ºF nighttime temperatures. With a decrease in freezing temperatures, the yearly number of freeze-thaw cycles tended to decrease at shallow pavement depths (<6 in.), whereas remained sporadic at deeper pavement layers. The decreases in freeze-thaw events at shallower depths were significant during the early and late winter months. However, the annual freeze-thaw events at the air temperature sensor level were randomly distributed throughout the analysis period.

Project Details
STATUS

Completed

START DATE

04/05/18

END DATE

03/31/23

FOCUS AREAS

Infrastructure

RESEARCH CENTERS InTrans, BEC
SPONSORS

Minnesota Department of Transportation

Researchers
Principal Investigator
Behrouz Shafei

Structural Engineer, BEC

Co-Principal Investigator
Brent Phares

Bridge Research Engineer, BEC

Co-Principal Investigator
Katelyn Freeseman

About the research

In 2018, the Minnesota Department of Transportation (MnDOT) constructed a pair of side-by-side bridges on TH 169 over Elm Creek, with glass fiber-reinforced polymer (GFRP) reinforcement used in one deck and conventional epoxy-coated steel reinforcement used in the other. To understand the behavior of GFRP reinforcement and compare the performance and durability of the GFRP- and steel-reinforced decks, the following efforts were undertaken: (1) collect structural behavior information and response characteristics of the two bridge decks under service loads; (2) examine the short- and long-term performance characteristics of the two bridge decks; and (3) assess the advantages of using non-conventional, corrosion-resistant deck reinforcement. From the outcome of this four-year monitoring program, both bridge decks behaved similar to each other and as expected. The GFRP-reinforced deck showed no unusual behavior or sign of deterioration compared to the steel-reinforced deck. Although similar patterns of surface and full-depth cracks were observed in both decks, the structural integrity of both bridges was found to be consistent with design specifications. The short- and long-term comparison of the decks indicated that the use of GFRP bars can be a promising alternative in bridge deck reinforcement.

Project Details
STATUS

Completed

START DATE

08/10/20

END DATE

04/30/23

FOCUS AREAS

Safety

RESEARCH CENTERS InTrans, CTRE
SPONSORS

Minnesota Department of Transportation

Researchers
Principal Investigator
Shauna Hallmark

Director, InTrans

Co-Principal Investigator
Nicole Oneyear
Co-Principal Investigator
David Veneziano

Safety Circuit Rider, LTAP

Co-Principal Investigator
Hossein Naraghi

About the research

As a low-cost countermeasure to rural intersection crashes, transverse rumble strips (TRS) provide an audible and tactile warning to drivers approaching an intersection with the primary goal of decreasing crashes that result from running a stop sign. The objective of this project is to evaluate the effectiveness of different TRS patterns on stopping behavior at rural stop-controlled intersections.

Eight rural intersections in St. Louis County, Minnesota, were selected as test sites. Milled-in rumble strips were installed at the sites that varied in terms of number of panels (2 or 3) and number of rumble strips per panel (6 or 12). Speed, traffic volume, and video data were collected at each site before, 1 month after, and 9 months after TRS installation to evaluate various crash surrogate metrics. The most significant metrics affected by TRS configuration included percentage of vehicles engaging in a full/rolling stop at the intersection, change in average speeds on the approach near the intersection, percent of vehicles traveling 45 mph or more, and percent of vehicles engaging in late braking. A qualitative summary of the various metrics suggested that the 3-panel, 12-rumble strip design performed the best.

Noise analyses were also conducted to assess whether the number of rumble strips per panel (6 or 12) affected exterior and in-vehicle noise. No significant differences in exterior noise were found, and both panels produced sufficient in-vehicle noise to alert a drowsy driver. As a result, noise was not a factor in selecting one panel type over another.

Project Details
STATUS

Completed

START DATE

05/18/20

END DATE

11/23/21

SPONSORS

Minnesota Department of Transportation

Researchers
Principal Investigator
Skylar Knickerbocker

Research Scientist, CTRE

Co-Principal Investigator
Zachary Hans

Director, CWIMS

About the research

Winter weather and its corresponding surface conditions impact the safety and mobility of thousands of motorists annually. Highway agencies spend millions of dollars in resources and personnel in an effort to ensure safe and efficient travel. One such strategy is to use dynamic message signs (DMS) that have been deployed across the state to alert drivers of conditions ahead based on data from roadside sensors. This type of advisory system can provide real-time information, allowing drivers to adjust their driving behavior to the conditions ahead.

The objective of this project was to analyze traffic behavior along a specially instrumented portion of the US 12 corridor under various winter weather conditions when advisory messages triggered by roadside pavement sensors were provided via DMSs between Delano and Maple Plain, Minnesota. Temporary traffic sensor data upstream and downstream of the DMS are used to evaluate traffic flow metrics during winter weather conditions as compared to baseline conditions.

In the eastbound direction, statistically significant reductions in mean and 85th percentile speeds of 3.5 mph and 2.9 mph, respectively, were identified. The westbound direction experienced mixed results, with a mixture of statistically insignificant changes as well as statistically significant increases and decreases in speeds. It is assumed that other factors were influencing driver behavior in this westbound direction. There were indications of positive effects on vehicle gaps when evaluating all events combined that were statistically significant but not when evaluating individual winter weather events.

Project Details
STATUS

Completed

START DATE

05/16/19

END DATE

10/29/21

FOCUS AREAS

Infrastructure

RESEARCH CENTERS InTrans, BEC
SPONSORS

Minnesota Department of Transportation

Researchers
Principal Investigator
Brent Phares

Bridge Research Engineer, BEC

About the research

The Minnesota Department of Transportation (MnDOT) funded two projects in an effort to mitigate anchor bolt connection loosening and develop improved pre-tensioning steps for its sign, luminaire, and traffic signal (SLTS) structures. The Phase I study proposed new pre-tensioning procedures, completed laboratory testing, did an in-depth literature review, and set up instrumentation. The next part of the work started by implementing the proposed procedures in the field and suggesting revisions to be investigated further in Phase II. Through this work, the structural monitoring objective was to better understand field fatigue forces on the anchor rods and develop a testing procedure to replicate field stresses accurately in the laboratory. In the Phase II project, lessons learned from both the field results and additional literature review were tested in the laboratory to balance the efficiency and efficacy of the revised pre-tensioning procedures. Feedback from stakeholders and experience from in-field inspections were considered for the revised procedures. Testing methods and conclusions were validated with finite element models and structural health monitoring. This final report brings all aspects of the work together and recommends improved procedures and additional studies.

TOP