Traffic data is generally available from state highway departments. In some cases, counties and municipalities may have more detailed information. The files below are from the Arkansas State Highway and Transportation Department.
The Bureau of Transportation Statistics (BTS), a part of DOT’s Research and Innovative Technology Administration (RITA), prepares and presents statistics in many formats. The ones listed below are especially useful.
The University Libraries has purchased books that can provide the basic details needed for more in-depth research. In addition, many of the major government documents as well as professional society resources have been cataloged when they are available electronically. So the Library Catalog, and WorldCat are two good places to identify basic information.
Manual on uniform traffic control devices (MUTCD) 2009 an electronic version has been cataloged.
There are 20 similar items (using the subject search: Traffic signs and signals -- United States -- Handbooks, manuals, etc). Several are earlier editions of MUTCD. But two other books might be useful enough to check out.
Traffic control devices handbook 2001 / [James L. Pline, editor]
Washington, DC : Institute of Transportation Engineers, 2001
TE228 .T72 2001 in Mullins Library 4th floor
Browsing on the shelf, leads to another book that might help in identification of the initial issues that need to be explored.
The Traffic safety toolbox : a primer on traffic safety / published by Institute of Transportation Engineers
Washington, D.C. : Institute of Transportation Engineers, c1993
TE228 .T735 1993 n Mullins Library 4th floor
There are many organizations, governmental and quasi-governmental, that are important places for publications in this field. Some, such as the Department of Transportation at both state and national levels, allow free access to their materials. Others, such as AASTHO charge for their publications. Please note the options below and add additional groups through the comment feature.