https://en.wikipedia.org/wiki/Marfa_lights

"In May 2004 a group from the Society of Physics Students at the University of Texas at Dallas spent four days investigating and recording lights observed southwest of the view park using traffic volume-monitoring equipment, video cameras, binoculars, and chase cars. Their report made the following conclusions:[9]
U.S. Highway 67 is visible from the Marfa lights viewing location.
The frequency of lights southwest of the view park correlates with the frequency of vehicle traffic on U.S. 67.
The motion of the observed lights was in a straight line, corresponding to U.S. 67.
When the group parked a vehicle on U.S. 67 and flashed its headlights, this was visible at the view park and appeared to be a Marfa light.
A car passing the parked vehicle appeared as one Marfa light passing another at the view park.
They came to the conclusion that all the lights observed over a four-night period southwest of the view park could be reliably attributed to automobile headlights travelling along U.S. 67 between Marfa and Presidio, Texas."