The entire length of I-380 between I-80 and US Hwy 30 at unpredictable intervals. Early spring and early summer usually brings a heavy enforcement period of a couple days of massive state, local and county enforcement using airplane, radar, & laser to stop many speeders at once. Often a long line of police vehicles can be seen parked on Airport exit (Exit 13) on-ramp to swoop down and stop speeders clocked by the State Patrol plane along the road a few miles south of the airport. Another popular spot to set up at is Exit 4 at North Liberty at the southern end of the route. North of Exit 4, there is no exit for 6 miles and south for 4 miles, making escape virtually impossible. Other times during the year, the state patrol plane and a couple vehicles seem to form a roaming speed trap up and down the length of the roadway, perhaps alternating between I-380 and I-80, moving around like a wolf pack looking for targets of opportunity. And, no hope for radar detection with the plane–silent and deadly. The only clue for detection is a small high-winged plane flying in the vicinity of the roadway, hardly a give away. If you see a number of patrol vehicles parked in a row at either Exit 4 or Exit 13, slow down and enjoy the view of many others pulled over.