Complex sentence: North of Interstate 355, the freeway is known locally as Illinois Route 53, or simply Route 53, as Illinois 53 existed before Interstate 290, but now merges with I-290 at Biesterfield Road.
Split into simpler sentences: North of Interstate 355, the freeway is sometimes known locally as Illinois Route 53, or simply Route 53, since Illinois 53 existed before Interstate 290. However, it now merges with I-290 at Biesterfield Road.