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Literature Searches and Literature Reviews for Transportation Research Projects: Examples of Effective Transportation Literature Reviews

Based on Transportation Research Circular Number E-C194, March 2015. "Literature Searches and Literature Reviews for Transportation Research Projects: How to Search, Where to Search, and How to Put It All Together: Current Practices."

Crack and Concrete Deck Sealant Performance

Crack and Concrete Deck Sealant Performance
Karl Johnson, Arturo Schultz, Catherine French, Jacob Reneson Minnesota Department of Transportation
Report No. MN/RC 2009-13, March 2009.
http://www.lrrb.org/media/reports/200913.pdf 

The appendix of this report includes a thorough summary of each study cited in the literature review. The review itself, however, effectively synthesizes this raw information into a more useful form that supports the overall paper’s purpose of defining the current state of the art regarding bridge deck sealants and crack sealers.

The literature review addresses bridge deck sealants and crack sealers in turn. Regarding deck sealants, it defines the two categories of sealants, the four performance measures used to evaluate sealants, and variables that affect performance such as concrete parameters and environmental conditions. The section on crack sealers discusses different types of sealers, their properties and application methods, performance measures, general trends in their effectiveness and variables affecting performance.

While there isn’t a specific “Gaps in Findings” section, this literature review effectively notes these gaps throughout the review, identifying areas for nearly every topic that existing research has not investigated as well as noteworthy limits to specific research projects cited. Of particular note is how the review identifies a shortcoming with a widely used deck sealant evaluation procedure and a suitable method to compensate for it:

It should be noted that the NCHRP Series II procedure, which is commonly used by vendors and state highway agencies to evaluate sealer performance, does not implement abrasion or freeze–thaw exposure to which sealers on bridge decks are frequently subjected. However, in determining the absorption properties of concrete sealers, a test was developed by Alberta Department of Transportation and Utilities which is essentially a modification of the NCHRP 244 procedure that incorporates abrasion (Kottke, 1987). Absorption is measured before and after abrading 0.04 in. off the faces of treated, cubic specimens to measure quantitatively the effect of abrasion on the absorption characteristics of sealers (p. 5).

The report clearly identifies the deck sealants and crack sealers that performed best for each of the performance measures, while noting how differences in test procedures can affect results. This provides useful information to support the report’s overall conclusions and recommendations. 

Snow Removal at Extreme Temperatures

Snow Removal at Extreme Temperatures
Michelle Akin, Jiang Huang, Xianming Shi, David Veneziano, Dan Williams
Clear Roads Program, Minnesota Department of Transportation, March 2013.
http://www .clearroads.org/downloads/Snow-Removal-Extreme-Temps-Final-Report.pdf

This report is immediately noteworthy for the thoroughness of its literature review in Appendix A, which makes up more than two-thirds of the report: 47 of 72 pages. Moreover, it includes international research and research from fields such as airports where snow-removal practices are different but potentially relevant to the work of state DOTs. The literature review also represents a clear topical organization, first providing an overview of literature available on various deicing chemicals with a focus on their physical properties, and then reviewing various strategies for clearing snow and ice from roads at low temperatures. 

Development of a Concrete Maturity Test Protocol

Development of a Concrete Maturity Test Protocol  

W. James Wilde
Center for Transportation Research and Implementation, Minnesota State University, Mankato Report No. MN/RC 2013-10, April 2013.
http://www.dot.state.mn.us/research/TS/2013/201310.pdf 

Field and laboratory studies were undertaken to evaluate the applicability of the concrete maturity method to establishing criteria for opening portland cement concrete pavements to traffic. The field study included visits to18 paving projects in Minnesota over a 3-year period. At these projects, different sensor types were evaluated. In the laboratory study, 2-in. mortar cubes were tested to develop sensitivity analyses related to the proportions of cementitious materials, water–cementitious materials ratio, and other mix components. The literature review chapter of the report summarizes and discusses the literature regarding (1) the maturity method in general and its use in concrete pavements in particular; (2) supplementary cementing materials; (3) maturity and flexural strength; and (4) various types of sensors for measuring maturity.

Quality of Life: Assessment for Transportation Performance Measures

Quality of Life: Assessment for Transportation Performance Measures  

Ingrid Schneider, Tian Guo, Sierra Schroeder
Minnesota Department of Transportation
Report No. MN/RC 2013-05, January 2013.
http://www.dot.state.mn.us/research/TS/2013/2013-05.pdf​

This report investigates a topic (the effect of transportation on quality of life) with relatively little published research and none that addresses the topic comprehensively. To provide context for the report, the researchers start with a broader assessment of research into quality of life. This assessment defines key terms relevant to the study as well as methodologies that have been used to measure and predict quality of life, with a number of demographic distinctions.

Connecting the literature to transportation requires something of a patchwork approach, collecting papers that illuminate some specific element of transportation’s effect on quality of life to give as complete a picture as possible. Chapter 2 reports on the limited assessments that have been conducted as well as the strengths and weaknesses of their methodologies, organized by the specific factor investigated. In doing so, the literature review clearly delineates what is known and what is not known about the subject.