Research News, February, 2009

Newsletter of the Iowa Department of Transportation's Research and Technology Bureau

Annual Report of Iowa Highway Research Board Research and Development Activities FY 2011, December 2011

The Highway Division of the Iowa DOT engages in research and development for two reasons: first, to find workable solutions to the many problems that require more than ordinary, routine investigation; and second, to identify and implement improved engineering and management practices. This report, entitled ―Iowa Highway Research Board Research and Development Activities FY2011‖ is submitted in compliance with Sections 310.36 and 312.3A, Code of Iowa, which direct the submission of a report of the Secondary Road Research Fund and the Street Research Fund, respectively. It is a report of the status of research and development projects in progress on June 30, 2011. It is also a report on projects completed during the fiscal year beginning July 1, 2010 and ending June 30, 2011. Detailed information on each of the research and development projects mentioned in this report is available from the Research and Technology Bureau, Highway Division, Iowa Department of Transportation. All approved reports are also online for viewing at: www.iowadot.gov/operationsresearch/reports.aspx.

Durable, Cost-Effective Pavement Markings Phase I: Synthesis of Current Research, June 2001

Pavement marking technology is a continually evolving subject. There are numerous types of materials used in the field today, including (but not limited to) paint, epoxy, tape, and thermoplastic. Each material has its own set of unique characteristics related to durability, retro reflectivity, installation cost, and life-cycle cost. The Iowa Highway Research Board was interested in investigating the possibility of developing an ongoing program to evaluate the various products used in pavement marking. This potential program would maintain a database of performance and cost information to assist state and local agencies in determining which materials and placement methods are most appropriate for their use. The Center for Transportation Research and Education at Iowa State University has completed Phase I of this research: to identify the current practice and experiences from around the United States to recommend a further course of action for the State of Iowa. There has been a significant amount of research completed in the last several years. Research from Michigan, Pennsylvania, South Dakota, Ohio, and Alaska all had some common findings: white markings are more retro reflective than yellow markings; paint is by-and-large the least expensive material; paint tends to degrade faster than other materials; thermoplastic and tapes had higher retro reflective characteristics. Perhaps the most significant program going on in the area of pavement markings is the National Transportation Product Evaluation Program (NTPEP). This is an ongoing research program jointly conducted by the American Association of State Highway and Transportation Officials and its member states. Field and lab tests on numerous types of pavement marking materials are being conducted at sites representing four climatological areas. These results are published periodically for use by any jurisdiction interested in pavement marking materials performance.At this time, it is recommended that the State of Iowa not embark on a test deck evaluation program. Instead, close attention should be paid to the ongoing evaluations of the NTPEP program. Materials that fare well on the NTPEP test de cks should be considered for further field studies in Iowa.

Final Report for Research Project HR-181, Macadam Base Shoulders, September 1981

Highway safety and pavement performance can be directly influenced by the type of shoulders that are constructed. Shoulder design alternatives have always been rather limited. Moreover, the use of some of the alternatives has always been restricted by funding limitations. This research project seeks to explore the use of modified macadam base construction for shoulders. This type of shoulder design could offer the designer another option when paved or stabilized shoulders are being considered. Macadam base construction has in the past been shown to be quite strong and free draining. Two macadam base shoulder designs were developed and constructed for this research project. A new roadway embankment and P.C.C. pavement were constructed on a section of US 6 east of Adel in Dallas County. The macadam base shoulders were constructed adjacent to the pavement as part of the project. The north shoulder was finished with a choke stone course and bituminous surface treatment and the south shoulder was finished with a two (2) inch layer of Type B Class I1 asphalt concrete. Macadam stone base shoulders can be built with relatively minor construction problems with comparable strength and less cost than asphalt treated base shoulders. The macadam stone base shoulders have performed well with very little maintenance necessary. The improved drainage substantially reduces deterioration of the pavement joints.