By providing broader dissemination of research and scholarship, open access increases its discovery, use, and impact. Research shows that open-access journal articles are cited 25% to 250% more often than journal articles with restricted access because faculty and students typically start their search for information with a Google search.  The Open Citation Project (OpCit) provides a bibliography of findings on the open access impact advantage, with links to the articles

Open access does not circumvent peer review, eliminate copyright, or encourage plagiarism.  Articles are peer-reviewed and published in journals. Authors have whatever rights they retained in their publishing agreements.  Open access serves to reduce plagiarism. When material is freely available, the opportunity for plagiarism to be recognized and exposed is much higher.

There are two paths to make your work available open access, known as green and gold:

• Green open access is making your work freely available on the web by posting it to a website or depositing it in a disciplinary or institutional repository, a practice known as self-archiving.  The Directory of Open Access Repositories (OpenDOAR) provides a list of repositories worldwide.  Carnegie Mellon's repository is Research Showcase.
• Gold open access is making your work freely available on the web by publishing it in a journal that provides open access.  Some journals make all their articles available open access; the Directory of Open Access Journals (DOAJ) provides a list.  Some open-access journals require authors or their institution or funding agency to pay article processing charges.  Many traditional (restricted access) journals provide an option to make your work available open access; exercising this option requires paying a fee

The term open access is widely used to describe material that is freely available on the web.  

• Gratis open access simply removes price barriers to access. All copyright restrictions remain in effect. Currently most open access resources are gratis open access.

• Libre open access removes both price barriers and unnecessary copyright and licensing restrictions, typically by attaching a Creative Commons license to signal what permissions the copyright owner grants the user. Increasingly materials are becoming libre open access. The Creative Commons offers six licenses that enable you to tell users what you allow and what you prohibit them to do with open access copies of your work. They also offer a tool that enables you to waive all copyrights and put your work in the public domain. The Berlin Declaration on Open Access requires libre open access.

Open access is an important policy issue. As of March 2011, open access was mandated by 47 funding agencies and 117 institutions.  In the United States, the first open access mandates occurred in 2008 with the National Institutes of Health (NIH) and the Faculty of Arts and Sciences at Harvard.  Many more agencies and institutions, including Carnegie Mellon, have adopted resolutions strongly encouraging open access. 

On a national level, most research is publicly funded, but the general public cannot easily access the results of research their taxes paid for.  In January 2011, the America COMPETES Reauthorization Act called for the creation of an interagency Public Access Committee to explore the feasibility of a broader open access mandate. The Committee is charged with coordinating federal science agency research and policies related to the dissemination and long-term stewardship of the results of unclassified research, including digital data and peer-reviewed scholarly publications, supported wholly, or in part, by funding from the federal science agencies.

Carnegie Mellon Provost Mark Kamlet is a strong supporter of open access.  He signed the 2002 Budapest Initiative on Open Access and was instrumental in developing the 2008 NIH open access policy.