Rumble Strips

Study of police accident reports in the mid 1980's revealed that Drift-Off-Road (DOR) accidents were the largest contributor to overall accidents on the Pennsylvania Turnpike. In searching for something to alert drivers that they were "drifting," a concept for a continuous shoulder rumble strip pattern emerged. A Federal Highway Administration report described several states' experiments with various shoulder rumble strip configurations. This work and some ideas from individual observations on the Turnpike led researchers to development and testing of a "Sonic Nap Alert Pattern (SNAP)". As the percent of accidents attributable to DOR continued to rise, testing of SNAP proceeded more seriously. A CalTrans report was encouraging in its description of a similar shoulder rumble strip pattern that had proved effective. In 1987, after testing various indented patterns, the first SNAP was installed on the PA Turnpike on a six-mile downgrade that had a history of DOR accidents. After an 18-month evaluation with only one reported accident, a decision was made to install SNAP over the full length of the Turnpike. A more recent summary of data from the first five SNAP installation projects showed a 70 percent reduction in DOR accidents. The SNAP design that was finally adopted was influenced by the Turnpike's vehicle mix and maintenance procedures, but broader applicability is suggested by its success. Reports have been received of other States and highways adopting the exact design and specifications for "SNAP.

< Back