About the research
In 2003, the states involved in the Midwest Smart Work Zone Deployment Initiative identified portable rumble strips (i.e., rumble strips that require no adhesive or fasteners, making them applicable for very short term work zones) as a high priority and solicited vendors for products to be evaluated by the study. Recognizing that no existing product strictly met the requirements cited in the solicitation, this research was proposed to develop a design for such a device based on aerodynamic and static exploration. The work began with wind tunnel and computational fluid dynamics (CDF) analyses to identify and estimate the critical forces acting on the roadway in the wake of a tractor-trailer. Vehicle simulation packages were used to examine the horizontal (i.e., sliding) force applied to the device by vehicle tires. Prototypes were developed and tested using a sound meter to monitor the sound levels inside the vehicle and both accelerometers mounted to a prototype strip and a high-speed video camera to monitor the interaction between the tires and the strips and to record the strips response to the impact during traversal.
Based on the analyses conducted in this work, a strip can be constructed that will resist the lifting forces in a truck wake, will not slide down the pavement, and will resist tipping even during heavy braking. Some bounce is inevitable. A segmented design was adopted to help minimize the effects of bounce, and a prototype was fabricated and tested to examine the performance.
In order for the strip to resist the lifting forces and the tipping forces, it must be fabricated from solid steel (or something with an equal or greater specific gravity), and needs to be at least 1 ft high in order to avoid requiring excessive widths. A 1.25 in. height is recommended, yielding a recommended breadth of 4 to 6 in. A 4 in. breadth prototype and a 6 in. breadth prototype were fabricated and tested with a loaded tractor trailer at 60 mph. Significant bounce was observed, but only in those elements struck by the tires. The adjacent elements did not move, resulting in no net translation of the strip as a whole. No tipping, sliding, or lifting due to negative pressures in the truck wake were observed.
Based on these results, the design developed in this study is a feasible solution for the need for portable rumble strips.