Keith Knappkknapp@iastate.edu email >
Director, Iowa LTAP
About the research
A large number of sign installation decisions based on engineering judgment are allowed by the Manual on Uniform Traffic Control Devices for Streets and Highways (the MUTCD). The information needed to make these installation decisions is based on a number of factors (e.g., MUTCD content, measured sign effectiveness). At the same time, signing represents a significant investment for transportation agencies.
The purpose of this project was to compile information on sign effectiveness and impacts (while also attempting to define the robustness and applicability of research results), as well as guidance on the installation, maintenance, and removal of signs to aid in decision-making. This study included a literature review, which critically evaluated, summarized, and rated existing research on a variety of static and/or enhanced regulatory and warning signs; a review of sign removal considerations; and a review of sign installation, management, and maintenance components. Material was found, reviewed, and summarized for the following signs: stop, yield, speed limit, horizontal alignment warning (e.g., chevrons, curve warning), playground, children at play, deer crossing, ice warning, road may flood, and enhanced stop, unsignalized intersection conflict warning, and signalized intersection advance warning systems. The guide also includes a description of legal considerations in Iowa connected to traffic control devices.
Based on the work completed during the project, it was concluded that the impacts of very few commonly used static signs have been studied and documented—to any great extent—with an approach that would meet the current state-of-the-practice for highly robust safety research results. However, this does not mean that a sign is not effective in the accomplishment of its various objective(s), including notification to drivers and increased awareness of regulations or hazards essential to roadway safety and operations.
Maintenance and management activities are also critical to ensuring that signs continue to meet the objectives that they were installed to accomplish. In addition, the legal information provided to the research team about traffic control devices indicated that, once a traffic control device has been installed, the jurisdiction must properly and adequately maintain it. The information summarized in this guide should be of value during sign-related decision-making on a case-by-case basis.