MINNESOTA DEPARTMENT OF TRANSPORTATION Engineering Services Division Technical Memorandum No TS-03 December 5, 2016

Transcription

1 MINNESOTA DEPARTMENT OF TRANSPORTATION Engineering Services Division Technical Memorandum No TS-03 December 5, 2016 To: From: Subject: Electronic Distribution Recipients Nancy T. Daubenberger, P.E. Division Director, Engineering Services Diverging Diamond Interchange Expiration This is a new Technical Memorandum and will remain in effect until December 5, 2021 unless superseded or published in the MnDOT Road Design Manual prior to that date. Implementation The design guidance on this Technical Memorandum is effective immediately for projects in the early stages of the preliminary design phase, and may be incorporated into other projects in a more advanced design phase based on programming and/or design constraints. Introduction The Diverging Diamond Interchange (DDI) or Double Crossover Diamond (DCD) is the innovative diamond interchange design that more efficiently facilitates heavy left-turning movements. The main difference from the standard diamond interchange is between the interchange nodes where traffic momentarily shifts to the opposite side of the road (left side). This crossover movement eliminates the conflict from the left-turning movements at the DDI. The greatest benefit of the DDI is to minimize the impact and delay caused by heavy left-turning movements. The DDI is a new form of interchange design which should be considered when evaluating alternative interchange design solutions. Purpose The purpose of this Technical Memorandum is to establish guidance for the design and implementation of DDI s. Guidelines Refer to the attachment for Design and Implementation guidance. Questions Any questions regarding the technical provisions of this Technical Memorandum can be addressed to either of the following: Douglas Carter, P.E., State Geometrics Engineer, MnDOT, at (651) Any questions regarding publication of this Technical Memorandum should be referred to the Design Standards Unit, DesignStandards.DOT@state.mn.us. A link to all active and historical Technical Memoranda can be found at To add, remove, or change your name on the Technical Memoranda mailing list, please visit the web page Attachments: Diverging Diamond Interchanges - Design and Implementation Guidelines -END-

2 Design and Implementation Guidelines Minnesota Department of Transportation December 2016

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4 Table of Contents Background... 3 Feasibility and Planning Considerations... 3 Multimodal Considerations... 4 Pedestrian and Bicycle Facilities... 4 Transit... 5 Geometric Design... 6 Crossing Angle... 6 Tangent Length... 7 Curve Radii... 8 Lane Width... 8 Shoulders... 8 Sight Distance... 9 Crossover Distance... 9 Safety Principles and Performance Safety Benefit Operational Characteristics Overview Study Results Signals, Signing, Pavement Marking and Lighting Signals Pavement Marking and Signing Lighting Public Acceptance References... 19

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6 Background The first diverging diamond interchange (DDI) concept design in the United States was introduced at the University of Maryland in At the time a novelty in the U.S., DDIs were a nearly 30-year-old European design. After the initial introduction a few transportation departments across the country began to discover the DDI concept and explore its feasibility. But it wasn t until 2009 that the first DDI opened to traffic on I-44 and SR 13 in Springfield, Missouri. The Minnesota Department of Transportation (MnDOT) began to implement DDIs in 2013 when the first one opened to traffic in St. Cloud on TH 15 and CR 120. A month later the Elk Run DDI opened on US 52 and CSAH 12 near Pine Island. Feasibility and Planning Considerations A DDI should be considered when traffic signalization at interchanges may not be able to adequately accommodate heavy left-turning movements. The first few DDIs constructed in the U.S. were retrofit projects. These DDIs enhanced the capacity of typical diamond interchanges without the need for additional lanes or expanded bridge footprints. One of the advantages of a DDI compared to a standard diamond is the traffic operational benefits. DDIs are most applicable when one of the left-turning movements is heavy and/or the through movements are unbalanced during peak hour periods. They also effectively accommodate a variety of traffic movement combinations so it is appropriate to consider a DDI as a viable alternative for new construction projects and in comparison with other conventional types of interchanges. When a DDI is a feasible solution it generally requires fewer lanes to accommodate the same traffic volumes compared to a standard diamond or a single-point urban interchange (SPUI). The required number of lanes are almost half that of a standard diamond or SPUI. That results in a smaller bridge structure footprint which is a source for significant cost savings. In fact, cost is the major factor that spurred the construction and implementation of the first few DDIs here in the U.S. Based on our experiences DDI project proposals have resulted in significant cost savings compared to other designs. Depending on the site, some costs such as right-of-way purchase and approach roadway construction will be incurred regardless of interchange type. Some advantages and challenges unique to DDIs are listed below. Advantages: Reduced conflict points Increased left-turn and overall capacity Reduced number of lanes(no exclusive left-turn lanes) Possibly reduced ROW impacts (close ramp terminals, shorter bridges) Traffic calming effect 2-phase signal operation Reduced project cost Easy U-turn capability for the mainline exit ramps Page 3 of 19 Challenges: May constrain through movement Driver unfamiliarity Off-ramp traffic crossing restrictions Impact to timing of nearby signals Integration of bike and pedestrian movements Public acceptance of new concept Lower capacity of nearby intersection may reduce effectiveness of DDI

7 Multimodal Considerations Pedestrian and Bicycle Facilities The unique geometry inherent with the DDI design calls for a careful consideration of the pedestrian and bicyclist movements and accommodations. The geometry of the DDI provides an alignment separation, allowing the separation space to be utilized as a pedestrian sidewalk or multi-use trail. When either of these is located down the center of the cross route, a traffic barrier is commonly used to provide for additional separation from traffic streams (Figure 1). Where barrier obstructs sight distance, its height may be reduced by tapering down from the Figure 1 DDI Center Pedestrian Sidewalk full height of the barrier down to the height needed to achieve the sight distance. Another option is to continue the sidewalk or trail accommodation along the outsides of the roadway just like any other type of interchange (Figure 2). Users can then continue on their side of the road in a way that s expected. The disadvantage to this configuration is that users must cross in the path of vehicles using free-right and free-left turns from or to the ramps, assuming the ramps are not signalized. Clear signing, striping, curb ramp design, and pedestrian signal head placement needs to be in place to minimize confusion for pedestrian movements because traffic movements in the interchange may be counter to user expectation. It is important to delineate the pedestrian path to ease wayfinding for all users, particularly on large raised median areas. Figure 2 DDI Pedestrian Facility Locations Page 4 of 19

8 Bicycles can also be accommodated on-road within a DDI, in a bicycle lane or on a right shoulder (Figure 3). If bike lanes or shoulders cannot be carried through the interchange they should be terminated far enough in advance so the bicyclists have the opportunity to either enter the motor vehicle lanes or enter a parallel shared-use path system. In this case consider slip ramps or driveways as entry points for on-road bicyclists. Figure 3 Typical Bicycle Accommodations Transit Transit facilities may also be accommodated along the center section of a DDI, as shown on this Bloomington, MN site (Figure 4). Creative traffic signal pre-emption and synchronized coordination allowed this light rail transit to operate within the interchange and adjacent intersections. Although it has not yet been implemented, similar arrangements with Bus Rapid Transit (BRT) lines should be possible. Figure 4 Light Rail Transit Accommodation at 34 th Ave in Bloomington, MN Page 5 of 19

9 Geometric Design One of the most distinct characteristics of a DDI is the crossover movement of vehicular traffic to the opposite side (left side) of the roadway in between the ramps of the interchange. This crossover movement happens at the signalized intersections at the ramp terminals on each side of the interchange (Figure 5). Drivers in the United States have been trained and accustomed to drive on the right side of the roadway. Shifting drivers to the left side is something new and is potentially confusing, so the geometric alignment needs to be designed properly to facilitate correct driver movement and behavior. Figure 5 Typical DDI crossover intersection As the driver approaches the intersection, reverse horizontal curves are used to shift them to the left side of the roadway. As much as possible the geometry of the roadway should direct the drivers naturally to the appropriate lanes as they approach and pass through the intersection. The horizontal crossover geometrics consist of three main interacting elements: crossing angle, tangent length approaching and following the crossover, and curve radii approaching and following the crossover. Crossing Angle The crossing angle (Figure 6) is the acute angle between lanes of crossing traffic at the intersection. It is very important in achieving the natural driving path for drivers. It orients them to the appropriate lane while decreasing the potential for confusion and wrong way movements. To balance the need for effective redirection of traffic and minimal right of way footprint, appropriate crossing angles should be used. The recommended approach is to use the largest crossing angle possible while balancing the need for the horizontal crossover geometry and design. There are two types of DDI crossovers: Narrow angle crossovers (30 to 40 degrees) and Wide angle crossovers (greater than 40 degrees). Page 6 of 19

10 Figure 6 DDI Intersection Crossing Angle The FHWA recommended crossing angle is 45 degrees; however smaller crossing angles such as 35 degrees tend to minimize the size of the center median and still provide enough space for a pedestrian refuge crossing within the median. In constrained situations with lower traffic volumes, angles smaller than 35 degrees can be considered. In this case pedestrian facilities would move through the perimeter of the interchange. Tangent Length The tangent length between the curves on the crossover serves as a positive guidance for the vehicles. It directs the drivers to align their vehicles to the appropriate lanes as they approach and pass through the intersection. This also aids in preventing path overlaps due to the use of reverse curves. At a minimum, the tangent length should span the intersection, providing 15 to 20 feet of tangent at the approaches and 10 to 15 foot tangent at the receiving roadway legs. This additional tangent length can also help reduce the negative impacts of tighter approach curvature and smaller crossing angles. These tangent segments are shown in Figure 7. Figure 7 Use of Tangents at DDI Crossover Intersection Page 7 of 19

11 Curve Radii The curves approaching and following the crossover should allow the design vehicle to navigate the interchange at the selected design speed, typically 20 to 30 mph, as well as accommodate turning movements at the ramp terminal (Figure 8).The 300 ft. radius curve is preferred as good practice, but radius as low as 200 ft. could be considered in constrained situations such as retrofit projects or low heavy vehicle volume. These curves should be designed to optimize crossing angle, tangent length, and sight lines while minimizing vehicle encroachment into adjacent lanes. Figure 8 Use of Curves Approaching and Following the Crossover Lane Width Lane width on a DDI crossover is something that is site specific. Approach roadway width should be maintained when geometry allows. Lane widths may need to be widened (13-16 feet) at the crossovers based on actual off tracking needs, or vane striping can be used. When dual turn lanes are provided, space should be available for the Design Vehicle to negotiate the turn in the right most turn lane. Shoulders Shoulder sections from the approaching roadways should be carried through the DDI interchange. Shoulder widths should be maintained and remain on the same side (right or left) as it passes through the crossover (Figure 9). This ensures that the functionality of the shoulder is maintained for cyclists, the shoulder meets driver expectation for emergency refuge, and it provides a consistent path for maintenance/snow removal operations. Figure 9 Shoulders Carried Through the DDI Crossover Intersection Page 8 of 19

12 Sight Distance Two areas of specific importance to a DDI are sight distance for vehicles making crossover movements and vehicles exiting from the limited access highway. The driver approaching or departing from an intersection should have a clear line of sight of the intersection, including any traffic control devices, and sufficient distance along the cross route to permit the driver to anticipate and avoid potential collisions. Particular attention should be given to the sight lines of vehicles turning from an exit ramp under yield control (Figure 10). For a driver making a right turn from the exit ramp of a DDI, the expectation is that traffic will be coming from the nearest lanes on their left. However, traffic is actually coming from the far left lanes since the direction of traffic is switched. These expectations have similar issues between drivers and pedestrians. Ensure that pedestrians and drivers of vehicles both have adequate sight lines between each other. Adequate sight distance should be provided at the crossover intersection. Provide at least 250 feet of intersection sight distance and an optimal approach angle of degrees in order to avoid driver sightline confusion with expected and actual oncoming traffic stream locations. Figure 10 Expected vs. Actual oncoming traffic sight lines Right and left turns merging into traffic streams are typically permitted to turn when gaps are available. Initial traffic evaluation indicates that traffic operations generally are not significantly affected by the addition of traffic signals for the left and right turn movements. However, when adequate intersection sightlines are not met, installation of additional traffic signals may be needed to mitigate sightline deficiencies. Crossover Distance Closely spaced ramp terminals can create a storage capacity problem for left turning vehicles in traditional diamond interchanges. The unopposed/free flowing left turns in a DDI solve this problem, but storage can still be a concern between the crossover intersections. Crossover distance should be calculated and the design adjusted as necessary to provide sufficient storage and facilitate appropriate signal cycle lengths to minimize impact of DDI to adjacent signalized intersections. Page 9 of 19

13 Safety Principles and Performance Safety Benefit A DDI design provides a safety benefit because it reduces the number of conflict points compared to traditional interchange types. By switching traffic to the left side between the ramp terminals, many of the most dangerous crossing conflicts due to left-turning movements are eliminated. As shown in Table A and Figure 11, DDIs have less conflict points than a conventional diamond and a single-point urban interchange. The overall reduction in conflict points for a DDI is almost half of a conventional diamond. Type Diamond SPUI DDI Diverging Merging Crossing Total Table A Conflict Points Comparison Figure 11 Conflict Points for Typical Interchange Types The safety study report, Safety Evaluation of Diverging Diamond Interchanges in Missouri, indicates that DDIs reduce crashes an average of 50%. They eliminate right-angle crashes and do not introduce significant new crash patterns. DDIs may be a new concept to many users, so design elements and geometry should create an environment that is intuitive for drivers, bicyclists, and pedestrians, meaning that positive guidance including medians, striping, channelization, and appropriate navigational signage is necessary. Page 10 of 19

14 Operational Characteristics Overview It is common to see traditional diamond interchanges suffer increased delay and a lower Level of Service (LOS) due to a specific heavy traffic movement, particularly left turns. An advantage of the DDI is that it removes the signal phase necessary to accommodate heavy volumes of left-turning vehicles. This allows the intersection to utilize two-phase signal timing, which increases capacity through shorter cycle lengths and decreased idle time. The traditional solution to high left turn demand is to build additional turn lanes and expand the footprint of the interchange. That is an expensive solution which often requires expanding the bridge for additional lanes. A DDI can greatly reduce project cost because it requires fewer lanes to manage the same amount of traffic than other comparable interchange designs. A Single Point Urban Interchange (SPUI) can also accommodate heavy left turn volumes, but requires the expense of a large structure to accommodate the design. However, despite its many advantages, a DDI is not suitable for all locations. Other intersection types should be considered in locations where: Projected through volumes are high, particularly when high concurrent through volumes are anticipated There are closely spaced adjacent intersections that may result in performance problems due to signal timing and traffic capacity issues The inability to allow through ramp traffic would impact staging, incident management, or bypasses for oversized vehicles The DDI would increase delay in a coordinated corridor Study Results A traffic study titled A Comparative Analysis of Diverging Diamond Interchange Operations (by Siromaskul & Speth) presented at the 2008 Institute of Transportation Engineers (ITE) Conference, modeled three interchange types (Diamond, SPUI, DDI) under four sets of traffic volume scenarios Figure 12). The results are as follows: A Heavy eastbound to northbound B Heavy westbound to southbound C Heavy through movements on crossroad D Heavy exchange movement Figure 12 - Interchange Volume Scenarios Page 11 of 19

15 Scenario DDI SPUI Diamond (sec/veh) (sec/veh) (sec/veh) A B C D Table B - Delay Comparison of Tight Interchange Concepts Scenario DDI SPUI Diamond A B C D Table C Lanes Required on Bridge for Tight Interchange Concepts Level of Service (LOS) Control Delay per Vehicle (sec/veh) Description A <= 10 Free flow operations B > Reasonably free flow operations C > Stable flow D > Approaching unstable flow E > Unstable flow F > 80 Breakdown in vehicular flow Table D Level of Service Criteria (Based on Highway Capacity Manual) Based on the combination of volume scenarios, the results for all three interchange types achieved an operational LOS D. However, the critical comparison should focus on Table C which shows the required number of lanes for each interchange type in order to accommodate the same traffic demand. This highlights the superiority of the DDI design in carrying higher left-turning volumes with a fewer number of lanes. The study entitled Design and Operational Performance of a Double Crossover Intersection and Diverging Diamond Interchange (by Bared, Edara, and Jagannathan), presented at the Transportation Research Board (TRB) in 2005, revealed that DDIs have twice the left-turn capacity than conventional diamonds. The DDI design does not have any exclusive left-turn lane, unlike the conventional diamond design, and the left-turners share the lane with the through movements. In this research, ramp terminal offsets of about 500 ft were assumed; however, the DDI design also works for shorter offsets with decrease in capacity on off ramps. Capacity of all other movements remained unchanged. In any case, the performance is still better than the corresponding conventional diamond design (See Table E on the next page). Page 12 of 19

16 Design Southbound Off-Ramp (veh/hr/ln) Northbound Off-Ramp (veh/hr/ln) Westbound (veh/hr/ln) Eastbound (veh/hr/ln) L L L R L R Diverging diamond (4 lanes) (L/T) (L/T) 600 Diverging diamond (6 lanes) (L/T) (L/T) 600 Conventional diamond *Note L=Left, T=Through Table E- Capacities of three different designs In general, the DDI Increases the overall capacity by 15% to 25% Increases the throughput by 10% to 15% Reduces intersection delay by 15% to 60% In addition, based on traffic operational analysis of DDI projects in Minnesota, MnDOT Metro District Traffic Unit has developed criteria for general traffic volume patterns where DDIs appear to be best suited. This involves comparing traffic volume patterns to a number of proposed DDI projects. With this set of observed characteristics, the following ratios should be considered as general DDI performance thresholds. When the ratio of the left turn volumes to the through volumes at the interchange is greater than 1. Here are some Metro DDI left/through ratios that support DDI consideration: o I-494 at 34 th Ave = AM 13.2 / PM 7.1 o TH101 at 144 th St = AM 3.5 / PM 2.0 o I-35W at CSAH96 = AM 1.2 / PM 1.8 o I-44 at MO13 = AM 0.74 / PM 0.44 (first DDI in Missouri) When the arterial mainline through volumes are on the low end (i.e. <400 veh) or imbalanced where you have definite inbound or outbound progression (i.e veh inbound 300 veh outbound). When Critical Lane Volume (CLV) for the DDI option is lower than the Conventional Diamond option in at least two of the four instances (AM/PM peaks at each of the ramp intersections). Page 13 of 19

17 Signals, Signing, Pavement Marking and Lighting Signals Placement and visibility of signals within DDIs need careful consideration (Figure 13). Because of the skewed geometry of the crossover intersection, proper signal angle installation plays an important role. Aligning the stop bars and the signal heads on the receiving lanes is also good practice. The traffic signals are located at each of the crossover intersections at the ramp terminals. However, it is also possible to provide signal-control at the right- and left-turn movements from the exit ramp terminal. This may be done to accommodate to higher traffic volumes, skewed and tight intersection geometry, limited intersection sight lines, or high pedestrian usage. As much as possible, good intersection geometry and ample intersection sight distance should be provided to avoid installing additional traffic signals which will incur higher project cost and additional maintenance. When pedestrian trails cross multiple signalized ramps, LOS for pedestrians should be taken into consideration. Signal timing should be optimized to minimize pedestrian delay, in order to promote compliance. Figure 13 Typical DDI Signal Locations Crossover intersection signal operation cannot serve two opposing through directions at the same time, so changes to the signal timing of adjacent traffic signals might be necessary to improve traffic operations. Through each DDI crossover signal, only one direction of traffic can come through, so the next intersection is affected by the staggered platoon effect. This changes the traffic coordination patterns, so adjacent traffic signals should be made part of any operational analysis, and depending on the impacts, additional signals beyond the adjacent signals can be included in analysis. Page 14 of 19

18 With careful evaluation and implementation, arterial coordination through a DDI is possible even with platoon staggering by optimizing progression in both directions. Progression can be maximized through the design of the crossover distance. Pavement Marking and Signing Although the DDI may operate in an unusual manner by momentarily shifting traffic, the pavement markings used are similar to other interchanges. It is a general practice to continue the yellow line on the left side of the driver upon crossing the intersection, and the white striping against medians on the driver s right side. Similarly, the white line should continue on the right side of the driver during the crossover movement (see Figure 14 as an example). Placement of stop bars, yield lines, and arrow lane-markings are standard applications. Stop bars are recommended to be staggered and perpendicular to the roadway tangent segment to provide a more positive vehicle orientation. Stop bars 24 inches wide are used to draw drivers attention to the stop bar at the crossovers and ramps and to discourage drivers creeping too far into the intersection. Placement of directional arrows should be considered to further emphasize the correct direction of traffic flow. Extension of dotted lane lines through the crossover intersection is also typically used to help guide motorists. When multiple turn lanes are present, dotted lane lines should be used to help guide drivers away from the dropped lane into the correct through lane. See most up to date pavement marking design guidance on the MnDOT Traffic Engineering Pavement Marking Typical Detail Sheets website select hyperlinks for both.dgn and.pdf files under Diverging Diamond. Figure 14 DDI Pavement Marking Page 15 of 19

19 Signs play an important role in facilitating proper use of DDI. Most of the guide, regulatory and warning signs used are similar to applications on a conventional diamond interchange. Examples of signs which are unique to DDI design are the KEEP LEFT sign and the use of directional arrows at the signal heads (Figure 15). Figure 15 DDI Overhead Signs Overhead signs (Figure 15), together with other signing and pavement markings (Figure 16) are used on the approaching roadway to direct drivers from the crossroad approaches through the interchange. At critical points Do Not Enter and Wrong Way regulatory signs should be installed to be visible to drivers. No signs should be placed on the inside of a left turn onramp movements in order to avoid signs being run over by the off tracking of semi-tractor trailers Figure 16 Sample Signing and Pavement Marking Plan Page 16 of 19

20 Lighting DDI s should be illuminated to meet recommended lighting standards based on IES and AASHTO guidelines for intersections and interchanges. It is preferred to use complete interchange lighting including lighting the ramps, intersection, and the tangent segment between the intersections. Additional pedestrian-scale lighting should be considered in any median pedestrian facilities. The presence of two medians can cause shadows and a feeling of enclosure. At rural DDIs a minimum of partial interchange lighting may be used with consideration given to complete interchange lighting. Public Acceptance Securing public acceptance for a new or unfamiliar interchange design can be difficult and time consuming. Studies and experience demonstrating improved traffic operations, improved traffic safety, and reduced cost may not be enough to convince people of the overall benefit to the community. Most communities will be unfamiliar with the DDI design concept, so efforts to effectively educate the community and communicate the DDI s advantages will be paramount. In order to alleviate misconceptions and promote support for the new design concept, community education and outreach cannot be overlooked and must begin as soon as possible. Some of the proven techniques to facilitate better understanding and overcome negative public perceptions include: Modeling and simulations Traffic engineers may know very well the LOS, delays, queues, crash history, and other technical data. However, traffic modeling and simulations are becoming very popular tools to convey to the general public how traffic will operate and what the driving, walking, and bicycling experience will look like or feel like. Videos - A drive-through video or simulation is also a very effective tool compared to the traditional aerial view pictures or layouts commonly used by engineers in public meetings (Figure 17). A simple video - especially for a new concept or idea - is often very effective when trying to disseminate a clear message. Often times, playing a video, prior to discussions of issues, is very helpful in providing a better initial understanding of the concept or idea. Project websites - Access to the internet and websites are one of the primary sources used when people are searching for information. Simple one-page brochures, handed out at public meetings are also very helpful for the general public to comprehend the DDI s effectiveness. Figure 17 Sample Simulation and Drive-Through Video Used in Public Presentations Variable message signs (VMS) prior and during construction can be critical to communicate expectations with the traveling public, including outreach for commuters who can t be reached door-to-door. Page 17 of 19

21 Social media These tools are also becoming a popular choice for the public to obtain information. Facebook and Twitter accounts are one of the leading channels where people provide feedback regarding transportation issues. This is consistent with what MnDOT has experienced. Public education Providing actual performance evaluations to mitigate misconceptions about the design can be helpful. For example, concern about the potential for wrong way moves is common. Providing a summary of the studies that have found no occurrences of wrong way movements and shown that DDIs are less difficult to navigate than what would be expected can be beneficial to obtaining stakeholder approval. Overall, recognizing there are multiple channels of communication is the key to success. Emphasizing and maintaining a simple and clear message regarding the traffic operations, traffic safety, and cost benefits has proven to yield positive results. Public-opinion studies indicate over 80% of the public becomes confident with the DDI a short time after opening. To date, there are a growing number of constructed DDIs in the U.S. There are currently 70 DDIs constructed across the U.S., and several others are in the planning and design stages. A partial list of known DDI locations is shown below in Table F. (Full list available at Interchange Location Date Opened 1 MO 13 Springfield, MO Jun 21, US National Ave Springfield, MO Jul 12, American Fork American Fork, UT Aug 23, Dorsett Rd Maryland Heights, MO Oct US Middlesettlements Rd* Alcoa, TN Dec 14, KY US 68* Lexington, KY Aug 14, Timpanogos Hwy Highland, UT Aug 14, SR Bangerter Hwy West Valley, UT Oct 23, Front Street* Kansas City, MO Nov 6, East American Fork, UT Nov 7, US MO 248 Branson, MO Jan 22, Ashford-Dunwoody Rd Dunwoody, GA Jun 3, MD Arundel Mills Blvd Hanover, MD Jun 11, US SR 221 Farmington, MO Sept 5, 2012 In Minnesota 22 New Olmsted CR 12 Oronoco, MN Sep 3, SR120 Stearns Cty Rd St Cloud, MN Oct 17, th Ave Bloomington, MN Nov 17, st Ave Rogers,MN Oct 29, I-35W & Hwy 96 New Brighton, MN Nov 12, 2015 Table F Partial List of DDI Locations in the United States Page 18 of 19

22 References J.G. Bared, P.K. Edara, R. Jagannathan, Design and Operational Performance of Double Cross Over Intersection and Diverging Diamond Interchange, TRB, Washington, DC, G. Chlewicki, New Interchange and Intersection Designs: The synchronized Split-Phasing Intersection and the Diverging Diamond Interchange. Anaheim, CA, S. Siromaskul, S. Speth, A Comparative Analysis of Diverging Diamond Interchange Operations. ITE Annual Conference, Anaheim, CA, Federal Highway Administration, Diverging Diamond Interchange Informational Guide, Report No. FHWA-SA , Utah Department of Transportation, DDI Guidelline - A UDOT Guide to Diverging Diamond Interchange, Utah Department of Transportation, June Missouri Department of Transportation, Diverging Diamond Interchange Performance Evaluation (I-44 & Route 13), Missouri Department of Transportation, Missouri Department of Transportation, Missouri s Experience with a Diverging Diamond Interchange: Lessons Learned, Missouri Department of Transportation, U.S. Department of Transportation, Driver s Evaluation of the Diverging Diamond Interchange, Tech Brief, Publication No. FHWA-HRT , Safety Evaluation of Diverging Diamond Interchanges in Missouri, Project TR201406, Report cmr15-006, Missouri Department of Transportation, Page 19 of 19