The 2009 Manual on Uniform Traffic Control Devices (MUTCD) contains ball-bank criteria, the most widely used method to determine advisory speeds. The MUTCD also establishes that, in general, advisory speeds shall be determined by engineering studies. The use of accelerometers and computational side friction factors are among such accepted kinds of studies. However, research has repeatedly shown that there are concerns associated with the consistency of the ball-bank indicator. A recent Oregon Department of Transportation research project, Safety Evaluation of Curve Warning Speed Signs, which was completed by researchers at Oregon State University (OSU), proposed a computational alternative to the ball-bank indicator known as the OSU Method. This method can be expected to improve both the consistency and safety performance of posted advisory speeds. This method’s underlying principle is that the recommended advisory speed should be such that it minimizes the expected number of crashes. The basis of quantifying expected crashes is a mathematical model that emerges from a statistical analysis of a sample representative of rural highways in Oregon. (Author/publisher)
Samenvatting