Background and current status of the development of updated minimum in-service retroreflectivity levels for traffic signs in the United States are described. A summary of the earlier work, conducted from the late 1980s to the mid-1990s, is provided along with descriptions of the relevant validation work. Related events that occurred in the late 1990s are described, and it is shown how, when combined with the assumptions and limitations of the earlier minimum retroreflectivity research, they resulted in a need for updated minimum retroreflectivity levels. The research related to the updated minimum retroreflectivity levels is summarized. A brief description of a second round of national minimum retroreflectivity workshops is also provided. The most recent set of recommended minimum retroreflectivity levels for traffic signs is presented along with a list of suggested research topics based on the limitations associated with the recommendations.

For more than a decade, the proportion of American Indians and Alaskan Natives killed in motor vehicle–related crashes (per population of 100,000) has been much higher than that of other ethnic groups in the United States. Between 1975 and 2002, the number of fatal motor vehicle crashes increased by 52.5% on Indian reservations, while the number declined by 2.2% nationally. Seat belt underuse, child seat restraint underuse, and operation of a motor vehicle under the influence of alcohol have been identified as key concerns for tribal transportation safety during various tribal safety summits and in the published literature. Without detailed data, identifying specific risk factors and developing effective solutions (as well as securing federal and state funding for safety programs) is difficult. This report summarizes the information available on crashes in tribal communities to generate a fact-based understanding of the status of transportation safety within these communities. Gaps in crash data and a study procedure to overcome these gaps are discussed to understand and work better to improve transportation safety on tribal lands. Results showed that readily available information could provide only a broad overview of the status of tribal transportation safety. For the major transportation safety concerns within a tribal community to be identified and addressed, data need to be obtained at the community level. For crash patterns and best practices to be identified, information should be aggregated from tribes that have successfully established a data collection procedure and have implemented safety programs.

Low-volume two-lane highways can be characterized by a wide range of physical features. Often the available crash data for these facilities are limited to fatal and injury crash information. It can be a challenge, therefore, to determine whether the select number of severe crashes observed along a corridor merits detailed safety evaluations and the associated investment of limited funds. The technique identified in this paper uses predictive method concepts developed with procedures consistent with those included in the AASHTO Highway Safety Manual but targeted only to low-volume roads and the number of observed fatal and injury crashes. For the purposes of this analysis, safety models are based on detailed crash and site data for low-volume highways in the state of Washington. A simplified procedure is then demonstrated to determine whether the number of severe crashes (fatal and injury) is significant enough to justify a detailed safety assessment and potential special safety enhancements on roadway construction projects or stand-alone safety enhancement projects for low-volume (≤1,000 vehicles per day) rural two-lane highways.