Overview
The goal of this page update is add additional guidance on the handling of elevation relative to overpasses in Illinois by revising the Major roads section of the Illinois wiki.
| This information is under consideration for the Illinois state wiki. It should not be considered official guidance. |
Content
US, State, and County Route Naming
The following naming conventions are used in Illinois for US, State, and County route naming.
US Highways 
US Highways (or routes) are named in Illinois using the standard US Road Naming guidelines. The base format of the name for these road types is:
- US-66 For U.S. Route 66
State Highways (Routes) 
Illinois state highways are named as follows:
- SR-23 For Illinois Route 23
- SR-23 S For Illinois Route 23, Southbound
- SR-23 BUS For Illinois Route 23 Business (note BUS must be in uppercase)
- SR-23 BUS N For Illinois Route 23 Business, Northbound (note BUS must be in uppercase)
- SR-23 ALT For Illinois Route 23 Alternate
- SR-23 ALT S For Illinois Route 23 Alternate, Southbound
County Highways 
County highways in Illinois are named with a "CH" prefix as illustrated below.
- CH-4 For County Highway 4
- CH-4 S For County Highway 4, Southbound
- Where Counties have highway designations beginning with a letter, the format looks like this:
- CH-T4 For County Highway T4
- CH-T4 E For County Highway T4, Eastbound
County Roads
Rural counties in Illinois employ a geographic coordinate system to name roads outside established communities. These roads are prefixed with a "CR." These names employ a number and a cardinal direction, general north (N) or east (E) of a specified locus. For example:
- CR-1000E Refers to county road 1000E
- CR-3000N Refers to county road 3000N
Township Roads
A select few counties employ township roads. Please consult with the state managers before editing names of township roads.