DDI Operations

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DDI Operations

  1. 1. DDI : The Ops Experience A Region 3 Perspective
  2. 2. DDIs in Region 3• American Fork – Pioneer Crossing and 500 E – Purpose built – Work great – Run free
  3. 3. DDIs in Region 3• Timpanogos Highway (SR-92) – Retrofit DDI – Under the freeway – Was opened with less than designed lanes – Works great (most of the time) – We’re retrofitting a trail into the DDI
  4. 4. DDI Operational Modes• Excess Capacity Mode (Low V/C ratio) – Run the intersections uncoordinated – Snappy response on detection – Low investment in timing – spend efforts on best possible detection – Low delay – easy to operate – American Fork DDIs
  5. 5. DDI Operational Modes• Design volume mode (moderate V/C ratio) – Run the intersections coordinated – Coordination is relatively easy – Low delay – fun to operate – Timpanogos Highway
  6. 6. DDI Operational Modes• Near Capacity Mode (high V/C ratio) – Coordination is crucial, difficult and time consuming – Interchange may “lock up” – Small changes = big delays – Large through movements are a problem
  7. 7. Observations• DDI vs. SPUI – Power out/Flash operations DDI is better – Off-peak operations DDI is better – Overcapacity ops – SPUI is better – Frontage road spacing – SPUI is better – Pedestrians – DDI works great with center sidewalk
  8. 8. Observations• With both intersections on same cabinet: – Diagram in cabinet shows indications – Camera Access in cabinet Indicators show which lights are on
  9. 9. Pedestrians• Timpanogos Highway – Adding trail to south side of interchange – Not impossible – but would be better in center – Adding peds on side rather than center can drive a decision to add a second controller and cabinet.
  10. 10. Acknowledgements• Eric Rasband and the I-15 CORE team• Matt Luker and the UDOT Traffic Management Division• Further Reading: – UDOT Diverging Diamond Interchange (DDI) Observations & Experience, Eric Rasband, Taylor Forbush and Kelly Ash

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