We were driving north on hwy 81. First saw the fireball from the Red River. We were traveling about 67 mph. Observed fireball traveling north along west side of 81. Last saw the fireball cross over to east side of hwy 81 as it passed town of Ryan, OKLAHOMA. It appeared to be low above treeline as it went out of site. Wife described the fireball as a lit up train in the low sky.