1. Interstate 435 and Front Street Interchange Improvements This presentation will probably involve audience discussion, which will create action items. Use PowerPoint to keep track of these action items during your presentation In Slide Show, click on the right mouse button Select “Meeting Minder” Select the “Action Items” tab Type in action items as they come up Click OK to dismiss this box This will automatically create an Action Item slide at the end of your presentation with your points entered.

2. Project Location

3. Purpose and Need for this project To provide safety improvements at the northbound and southbound exits from I-435, within the interchange on Front Street and the entrance ramp onto southbound I-435.

5. Initial Concepts We Reviewed Single Point (SPUI) Half-Cloverleaf Roundabout Tight Urban Diamond (TUDI)

6. Single Point (SPUI)

7. Problems with a Single Point design Required extensive reconstruction of I-435. Costs for additional right-of-way and construction were very high, about $31 million.* We had concerns about how long it would take trucks to clear such a large intersection. *B ased on 2002 estimates.

8. Half-Cloverleaf

9. Problems with a Half- Cloverleaf design Required large amounts of new R/W. Costs for additional right-of-way and construction were very high, about $37 million.* We had concerns about the trucks being able to accelerate from the loop ramps onto the freeway. *B ased on 2002 estimates.

10. Roundabout

11. Problems with a Roundabout design Did not perform as well as other alternatives. We had concerns about the operation of the trucks in the roundabout (two trucks likely would not enter a roundabout at the same time, reducing capacity). Costs for additional right-of-way and construction, about $10 million.* *B ased on 2002 estimates.

12. Tight Urban Diamond (TUDI)

13. Problems with a Tight Urban Diamond design Required considerable reconstruction of I-435. Did not work as well as the SPUI or half-cloverleaf. Costs for additional right-of-way and construction were high, about $28 million.* *B ased on 2002 estimates.

14. Initial Design

15. The existing interchange is very similar to a TUDI, with I-435 over Front Street. The initial preliminary design included: Adding lanes to the off ramps with double and triple left turn lanes. Adding lanes to Front Street between Universal and Corrington with traffic lanes behind the bridge piers.

16. Problems with the initial design The life of the capacity improvements were limited. This design would probably fail within 10 to 15 years. The Levels of Service were D, E and F. Costs for additional right-of-way and construction were still somewhat high, about $11 to $12 million.* This design has 45 conflict points within the entire interchange. *B ased on 2005 estimates.

17. Conflict Point Diagram - TUDI

18. Problems with the initial design Triple left turn lanes were needed for the northbound to westbound movement. This is not desirable with 11% trucks during peak hour. (Off peak has about 30% trucks.) Seven lanes were needed under the bridges, requiring construction of lanes and retaining walls behind the bridge piers in existing sand fills. This would be difficult to build. The trucks required large turning radii to achieve capacity improvement. This limited vehicle storage between the signals.

19. A Practical Design Solution A Diverging Diamond Interchange or DDI

20. Diverging Diamond Design Link to DDI overhead video Link to one of the drive thru videos

21. Advantages of using a DDI at this Location The DDI doubles the capacity of the left turn lanes and eliminates the need for the triple left turn. The double left turn should be safer than a triple with high truck volumes. Levels of Service are A, B and C. This design reduces the number of lanes required under the bridge to four, eliminating the need to build retaining walls.

22. Advantages This also reduces the number of lanes needed on Front Street beyond the interchange. This DDI design has more storage room between the ramp signals. (550’ vs 350’) This design will also provide better sight distance. Drivers on the ramps don’t have to look through bridge columns to see on-coming traffic.

23. Advantages It incorporates roadway features which calm traffic and reduce speeds while maintaining capacity. This should result in fewer and less severe crashes. Although wrong way entry into opposing lanes is possible, wrong way entry onto the ramps and the interstate will be almost eliminated. The DDI has 21 conflict points compared to 45 with the initial design.

24. Conflict Point Diagram - DDI

25. Advantages The smaller ramp intersections mean vehicles will have shorter clearance times resulting in less exposure and safer conditions. The DDI design has reduced the cost of the project.

26. Estimated Costs * Initial DDI Construction MoDOT$ 6,763,000 $4,097,000 Kansas City$ 103,000 $ 71,000 Right of Way MoDOT $ 1,823,000 $ 625,000 Kansas City$ 2,045,000 $ 667,000 Utility Relocations MoDOT$ 600,000 $ 312,000 Total Costs $11,334,000 $5,772,000 *B ased on 2005 estimates.

27. Disadvantages of a DDI Driver expectations. We need more extensive public involvement. Pedestrians have to cross free-flowing ramps (or the crossings need to be signalized as at this location). There is very limited accident history available. We need additional signing, lighting and pavement markings.

28. DDI One construction season Length of Construction Two construction seasons TUDI

29. Conclusion The DDI will improve safety and capacity of the existing interchange, at less cost and with a shorter construction schedule. It will also provide valuable information on function and safety that will allow MoDOT and FHWA to determine if use of the DDI design at other locations is feasible.