Alternate A: Diverging Diamond Interchange

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• US 61 southbound movement will be two lanes through the interchange.
• US 61 northbound will be one lane across the bridge.
• MO 74 will be realigned to connect into the west side of the DDI.
• US 61 and Silver Springs intersection will be upgraded to a 2-lane roundabout in an effort to improve safety. Access to current arterial routes will remain.
• The existing MO 74 connection under I-55 would be eliminated.

Advantages

• Conventional interchange ramps reduce confusion by aligning with driver expectation.
• Improved merging opportunity for I-55 southbound.
• MO 74 realignment provides a more direct connection.
• Supports heaviest traffic movements.
• 2 phase signals improve operation and reduce delays.
• Reduces wrong-way movements to I-55.
• Similar interchange being used in Center Junction on I-55 at Exit 99.

Disadvantages

• Requires traffic signals. 
• Off-ramp traffic can’t re-enter the freeway for motorists who take wrong exit.

Alternate B: Dogbone Interchange

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• Western roundabout is 2 lanes to accommodate for heavy traffic flow to I-55 southbound.
• Eastern roundabout is 1 lane to US 61 northbound and 2 lanes for US 61 southbound.
• I-55 northbound to US 61 northbound will bypass the roundabout in a dedicated, free-flow lane.
• MO 74 will be realigned into the western roundabout. 
• US 61 and Silver Springs intersection will be upgraded to a 2-lane roundabout in an effort to improve safety. Access to current arterial routes will remain.
• The existing MO 74 connection under I-55 would be eliminated.

Advantages

• Roundabouts eliminate need for traffic signals and offer safety benefits over traditional intersections.
• Improved merging opportunity for I-55 southbound.
• MO 74 realignment provides a more direct connection.
• Similar to conventional interchange layout.
• Off-ramp traffic can easily re-enter the freeway for motorists that take wrong exit.
• Crashes are less severe at roundabouts than at signalized intersections.

Disadvantages

• Can take motorists longer to learn how to use roundabouts.

Alternate C: Foldover Interchange

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• MO 74 will be realigned into the interchange and connect to the roundabout.
• Motorists traveling from US 61 southbound to I-55 southbound will travel through the folded loop ramp and merge onto I-55.
• Motorists traveling from US 61 southbound to I-55 northbound will gain access to the entrance ramp at the Silver Springs roundabout.
• US 61 and Silver Springs intersection will be upgraded to a 2-lane roundabout in an effort to improve safety. Access to current arterial routes will remain.
• The existing MO 74 connection under I-55 would be eliminated.

Advantages

• Elimination of northbound ramp intersection reduces crash exposure.
• Roundabouts eliminate need for traffic signals and offer safety benefits over traditional intersections.
• Extended merging opportunity for I-55 southbound.
• MO 74 realignment has smaller footprint with improved access to parcels west of I-55.

Disadvantages

• Less direct access from MO 74 to I-55 northbound.
• Loop ramp offers slower travel speeds and shorter merge opportunity near the intersection prior to the I-55 merge.
• Access from I-55 northbound to MO 74 westbound would require a U-turn at the Silver Springs roundabout.
• Additional bridge needed for I-55 southbound exit ramp.

Alternate D: Minimum Build

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• Maintains the existing interchange configuration.
• Replaces the US 61 southbound bridge to MO 74 and I-55.

Advantages

• Lowest cost

Disadvantages

• Does not address connectivity, safety or congestion issues