Small sign and small-sign support systems account for a substantial investment by federal, state and local agencies. For the past 20 or more years these systems have been tested for crashworthiness. Many small-sign systems had been tested and approved on the basis of previous specifications. For the most part, these tests were conducted with different vehicles and sometimes at different impactspeeds than those required by current specifications. Retesting of current systems will undoubtedly be required as new specifications are released. A rationalethat can be used to predict impact performance for sign installations that havebeen tested previously with a different size and class of vehicles is presented. In spite of the variability in test parameters, it appears that an energy formulation will provide estimates, not only for the current standard, but also for any future vehicle weights or impact speeds. Most sign systems, breakaway or not, appear to follow a linear relationship between kinetic energy and impact velocity. Recent tests, for the most part, support this theory. The one notable exception to the linear fit is the triangular slip base. This system, because of its unique failure mechanism, is more appropriately modeled by a cubic equation of best fit. The estimated changes in velocity could be useful for recertification of existing sign systems as well as for extrapolation between single- and multiple-post systems. If additional tests are required, the estimated changes in velocity will indicate which tests are critical, thereby allowing for the possibilityof fewer certification tests. This paper appears in transportation research record no. 1258, Roadside safety 1990.
Abstract