Complex sentence: The western terminus of I-270 is at the interchange with I-25 and US 36 at Welby and heads eastward to an interchange with I-76, where the mileposts reset because of a previous freeway extension.
Split into simpler sentences: The western terminus of I-270 is at the interchange with I-25 and US 36. It heads eastward to an interchange with I-76, where the mileposts reset because of a previous freeway extension.