I-84 Mobility Improvement Study

The I-84 Mobility Improvement Study identified targeted strategies that can improve interstate traffic flow, reduce congestion and support the region’s continued growth. To address these priorities, ITD evaluated several options:

• Lane additions
• Auxiliary lane additions
• Interchange ramp improvements
• Real-time traffic management strategies such as travel time information, ramp metering and incident detection

Why This Study is Needed

Traffic volumes on portions of I-84 have increased by an average of almost 15% from 2019 to 2025. Additionally, on- and off-ramps experience significant congestion during peak hours, causing backups on nearby roads and on I-84.

By 2055, daily traffic volumes on key segments of I-84 are projected to grow by nearly 50%, increasing congestion and travel delays if improvements are not made.

• Garrity Boulevard Interchange to Ten Mile Road Interchange: 47% increase (132,800 to 195,100 vehicles per day)
• Ten Mile Road Interchange to Meridian Road Interchange: 44% increase (136,800 to 196,400 vehicles per day)
• Meridian Road Interchange to Eagle Road Interchange: 38% increase (148,600 to 204,500 vehicles per day)
• Eagle Road Interchange to Flying Wye Interchange: 31% increase (166,200 to 217,300 vehicles per day)

Recommended Improvements

ITD recommends a combination of mainline lane and interchange ramp improvements to address traffic flow on I-84:

• Keep four lanes of traffic on I-84 in both directions while adding auxiliary lanes between interchanges.
• Widen interchange on- and off-ramps to two lanes.
• Add two westbound lanes from the Flying Wye to the Eagle Interchange to improve capacity.
• Replace the Five Mile Overpass with a new bridge to accommodate six lanes in each direction on I-84 (under design).

ITD developed these recommendations through a comprehensive evaluation of each alternative, analyzing projected traffic volumes and traffic counts, safety improvements, right of way impacts and overall cost effectiveness. This data-driven approach identified the solutions that provide operational, safety and investment benefits.

Future Benefits

By 2055, these recommendations are expected to:

• Improve eastbound morning travel times by nearly 5 minutes when compared to not making improvements.
• Improve westbound evening travel times by up to 10 minutes when compared to not making improvements.
• Reduce bottlenecks and congestion to allow more vehicles to enter the interstate.

Next Steps

ITD has developed a phasing plan for constructing the recommended improvements, beginning with the Flying Wye Interchange to Eagle Interchange portions of I-84 and then moving west. ITD will proceed with design work in 2027 before construction begins.

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