Wind Shear's tunnel is a closed air circuit, temperature controlled system built around a rolling road. The rolling road, akin to a giant treadmill, is 3 meters wide by 9 meters long and accommodates full size cars. Air and rolling road speeds are coordinated up to 80 metres per second (260 ft/s). Air temperature, critical to repeatable data collection, is maintained at a constant 75 °F (24 °C)), plus or minus one degree. Air is moved through the massive 15,000 sq ft (1,400 m2) air circuit at the maximum rate of 47,500 cu ft (1,350 m3) per second by a 5,100 hp (3,800 kW) motor and 29 carbon fiber blades 22 feet (6.7 m) in diameter. In the wind tunnel industry, size is everything. The blockage effect is the condition where air flow in the wind tunnel is partially blocked by the vehicle. The blockage becomes more critical as the cross section of the test vehicle increases relative to the size of nozzle and airstream. As the vehicle increases in size relative to the nozzle, test data become less reliable as increased blockage affects the quality of the actual windstream. Windshear's solution was to build a sufficiently large air circuit. Nozzle size is a relatively large 180 square feet (16.7 square meters).