The author's previous study of the 55 mph speed limit identifies the various costs and benefits and provides a framework for viewing the resulting trade-off between gasoline cost savings, traffic fatalities, and travel time. New data sources will permit more accurate measurement of speed-limit effects than was possible with the 55 mph limit. If the National Research Council's findings for the 55 mph limit are applicable, the trade-off will turn on the fatality risk and personal travel-time effects and hence on the values of life and time. For research purposes, speed monitoring should be continued on the 65 mph roads and on those still posted at 55 mph. When sufficient data are available, several methods should be used for safety impact assessment, and the results compared. These methods include multiple regression models, autoregressive models, and treatment-control approaches. Though not strictly necessary for the analysis, an indepth study of rural interstate accidents would be useful. Commentaries accompanying the paper suggest some other factors that might be considered in evaluating speed limits. 3 tables, 8 notes, 18 references.