Complex sentence: There have long existed plans for a four-lane limited access bypass to be constructed west of downtown Algonquin, intended to alleviate traffic at what is currently the most congested intersection in McHenry County, and divert through traffic.
Split into simpler sentences: There have long existed plans for a four-lane limited access bypass to be constructed west of downtown Algonquin. This would alleviate traffic at what is currently the most congested intersection in McHenry County, and divert through traffic.