Welcome to Chicago Oversize Permit Agency In Illinois Need an Oversize permit? Chicago Permits, provides oversized vehicle permits services. Contact one of our permit agents today!Oversize and Overweight Permits Agency In Illinois Need an Oversize permit? Chicago Permits, provides oversized vehicle permits & services. Contact one of our permit agents today. These vehicular permits limit the routes, times of operations, maximum rate of speed and other conditions deemed necessary by the State. This website provides general information and guidance pertaining to the issuance of OS/OW permits