Park in the Wilmington University parking lot - NOT off of the entrance to Rt1. Cache is a traditiional micro with log only in a strip of woods. The Pennsylvania Turnpike developed and installed an innovative type of shoulder rumble strip called the Sonic Nap Alert Pattern (SNAP). Tires rolling over the strip produce a distinct warning sound and vibration alerting drowsy or inattentive drivers that their vehicles are drifting along the shoulder of the roadway. SNAP was developed by Neal E. Wood, P.E., Pennsylvania Turnpike Bridge Engineer (retired), who studied accident reports looking for possible engineering modifications to improve safety. He started with safety near bridges, but noted and kept track of the high percentage of accidents caused by drivers drifting off the road with no real explanation except inattentiveness or drowsiness. In 1984, Wood first envisioned SNAP as a narrow, continuous strip of grooves along the right side of the roadway. Other states were trying various rumble strips on roadway shoulders as warning devices for drivers whose vehicles stray off the road (1, 2); many of these patterns were raised strips or grooves that were installed across the full width of highway shoulders, which adversely affected use of shoulders by service vehicles and could catch snowplow blades. Therefore, at an abandoned stretch of turnpike, Pennsylvania Turnpike engineers tested only narrow and recessed rumble strip patterns with varying lengths and depths and selected an effective design with enough sound and vibration to be perceptible in a truck cab and yet not too severe for cars or motorcycles (3). All tested patterns used an indentation spacing of one every foot (.305m) along the direction of travel so vehicle tires could not miss them at typical departure paths. This length between grooves was selected based on vehicles drifting off at a shallow 3-degree departure angle, striking a succession of indentations to produce a tone with enough duration to awaken a drowsy driver. All test patterns were 16 in. (40.64cm) wide, (transverse to the direction of travel) so that wide truck tires would drop in enough indentations along any likely departure path. By trying several depths, it was found that 0.50 in. (1.27cm) was deep enough for tire drop to produce an alerting sound, provided that the opening (length in the direction of travel) was large enough for various sized tires. Grooves 2 in. (5.08cm) were not heard over a 79 decibel noise level in truck cabs. Openings 4 in. (10.16cm) long with 8 in. (20.32cm) between produced sound audible in both cars and trucks with 86 decibels in a truck cab at 65 mi/h (105 kph). After the first highway installation, project contractors asked to try milling SNAP in existing shoulders rather than rolling or impressing it in hot asphalt during paving. The milling head was 24 in. (60.96cm) in diameter, which produced a 7 in. (17.78cm) opening while grinding to the specified 0.50 in. (1.27cm) depth. This modified design with 7 in. openings 5 in. (12.7cm) apart was 3 decibels louder (at 89 decibels) than the original rolled-in depressions with 4 in. (10.16cm) openings, which is a perceptible difference.