The goal of this page update is reorganization of the Major Roads section of the wiki.
|This information is under consideration for the Illinois state wiki.|
It should not be considered official guidance.
Illinois follows the general road naming and road type guidelines of the USA.
US, State, and County Route Naming
Exceptions to the USA road naming linked to above within Illinois are:
- In July,2013, all US Hwy XXX have been changed to US-XXX.
- State Rte XXX is being changed to SR-XXX format.
- CR-XXX will be used where applicable. Most have a Primary Street name, so this would only apply to an Alternate Field entry.
Road Type (Functional Classification)
Illinois follows standard USA guidance for assignment of road type assignment. It is important to remember that the interactive IDOT map used a base map that may have yellow colored roads that are not collectors. Minor collectors are bright yellow.
= Road Lock Standard
Illinois follow the Great Lakes Region road locking standard.
The provisions for turning in Illinois are defined in Rules of the Road, in Illinois Compiled Statutes 625 ILCS 5/11. In this wiki section we cover two specific situations: Left turns across medians and U-Turns.
Left Turns across Medians
Left turns across paved non-curbed medians are allowed in Illinois, defined in 625 ILCS 5/11-708 (e).
The Illinois Department of Transportation (IDOT) defines several types of medians in Bureau of Design and Environment Manual Ch. 34, Cross Section Elements:
- Flush - A median which is adjacent to traffic lanes and on the same plane as the lanes. These are painted on the pavement surface.
- Depressed - The median between opposing traffic lines is slightly below the elevation of the traffic lanes. It is also designed for drainage and storage of plowed snow.
- Raised-Curb - The curb on these medians is greater than two inches in height.
- Traversable - This type of median has a curb two inches in height.
A Two-Way Left Turn Lane (TWLTL) is typically a flush median. IDOT allows a traversable median to be used as a TWLTL in place of a flush median.
In Illinois, U-Turns can be performed unless specifically prohibited by law. Illinois statute defining the limitations on U-Turns is 625 ILCS 5/11-802 and can be reviewed in the Illinois Secretary of State Rules of Road booklet.
U-Turns can be enabled when editing by enabling the U-Turn flag or at box (#) and partial-box (H) intersections when the median segment is more than 15m in length (See Avoiding U-turns in box and partial box intersections).
When considering enabling a U-Turn, do so only if there is a strong potential to provide improved routing. Some examples of U-Turn implementations are:
- Where driveways or parking lots are connected to a median-divided roadway and doing so would eliminate complex routing to reach the proper side of the road.
- At both connected end-points of a single segment parking lot or gas station to provide an optimal exit route.
Before enabling a U-Turn on public streets, these conditions should be met:
- No traffic control devices posted prohibiting the movement.
- The movement may not be performed on a curve.
- The movement may not be performed on a hill or incline.
- A driver must be able to see in all directions on all roadways a at least 500 feet (153 meters).
- The turn must be able to be completed as a single continuous movement. While not a legal requirement, is best practice for safer navigation.
- At least 15 meters (49 feet) exist from the left edge of the legal departure lane to the right edge of the destination lane, including any median to the left of the departure lane, to allow single continuous movement.