A5−5: Additional Shoulder Thickness
All new construction or reconstruction projects on truck routes on the State system that involve the construction of new shoulders shall meet thickness requirements that are included in Illinois Department of Transportation's standard specifications:
• 2−lane major principal arterials – These highways should normally have 8' to 10' paved shoulders. If the 20−year projected traffic exceeds 2,000 multiple unit trucks (MU) per day or 10,000 Average Daily Traffic (ADT) the shoulders shall be constructed to the same thickness as the pavement. The 2,000 MU threshold is based on the traffic that would require a shoulder thickness greater than 200 mm to handle the occasional load.
• 4−lane highways – When the 20 year projected traffic exceeds 3,000 MU's per day or 25,000 ADT, shoulders shall be built to the same thickness as the adjoining pavement. If the expected Vehicles Per Hour (VPH) exceeds 1,700 the shoulder shall match the thickness of the pavement. When anticipated that the shoulder will be used for an extended period of time (greater than 3 years) during the design life of the pavement, the shoulder shall be designed to pavement standards, utilizing the same pavement design, details, and materials as the mainline pavement.
REASON(S) FOR ADOPTING:
Additional shoulder thickness is intended to allow the shoulders to be used, if necessary, to carry traffic during construction improvements and incident management.
The shoulder is utilized during construction projects and incidents. Traffic can be shifted to maintain the number of lanes and minimize the effects of work zone activity.
MOST APPLICABLE LOCATION(S)/PROJECT(S):
2−lane major principal arterials, 4−lane highways, Interstates, and expressways that are truck routes.
RELATED BEST PRACTICE(S):
Reinforcing Shoulders (Practice G1-3)
STATE(S) WHERE USED:
Tim Kell, Illinois DOT Bureau of Construction
Phone: (217) 782−6667