Diverging Diamond Diverging Diamond Interchange 101 Interchange 101 14 th Annual ACEC-KY FHWA KYTC Partnering Conference August 11 th , 2009 Presented By: Presented By: Scott Wolf, PE, PLS Scott Wolf, PE, PLS
What is a Diverging Diamond What is a Diverging Diamond Interchange (DDI)? Interchange (DDI)? • It’s a It’s a non-traditional design to non-traditional design to accommodate left-turning accommodate left-turning movements at movements at signalized, grade separated interchanges while signalized, grade separated interchanges while eliminating the need for left-turn phasing of eliminating the need for left-turn phasing of the traffic signals the traffic signals • Also known as a Double Also known as a Double Crossover Crossover Diamond Diamond (DCD) (DCD)
What is a DDI? (Continued) What is a DDI? (Continued)
Where did the DDI come from? Where did the DDI come from? • The DDI originated in France in The DDI originated in France in the 1970’s the 1970’s • Until recently, the only known DDIs were located Until recently, the only known DDIs were located in France: in France: – Versailles Versailles – Le Perreux sur Marne Le Perreux sur Marne – Seclin Seclin
A13 & RD182 A13 & RD182 Versailles, France Versailles, France Only 11 light injury Only 11 light injury crash crashes repor s reported in ted in 5 5 years compared to years compared to an an average of 23 average of 23 fatal/injury cras fatal/injury crashes of a s of a typical DI in typical DI in the the USA USA
D45 & A4 D45 & A4 Le Perreux sur Marne, France Le Perreux sur Marne, France
A1 & D549 A1 & D549 Seclin, France Seclin, France
Why a Why a Diverging Diamond? Diverging Diamond? • Improve Improved operational bene operational benefits with two phase fits with two phase signal operation since left-turn phase is eliminated signal operation since left-turn phase is eliminated
DDI Signal Phasing DDI Signal Phasing
DDI Signal Phasing (Cont.) DDI Signal Phasing (Cont.)
DDI Operational Benefits DDI Operational Benefits • Research has shown that compared to a traditional Research has shown that compared to a traditional diamond interchange, the DDI: diamond interchange, the DDI: – Reduces intersection delay by 15% – Reduces intersection delay by 15% – 60% 0% – Increases throughput by 10% – Increases throughput by 10% – 30% 30% – Increases overall capacity by Increases overall capacity by 15% - 15% - 25% 25% • A DDI accommodates heavy left-turn volume A DDI accommodates heavy left-turn volumes s onto ramps and from off-ramps onto ramps and from off-ramps • A DDI accommodates moderate or unbalanced A DDI accommodates moderate or unbalanced through volume through volumes
Why a Why a Diverging Diamond? Diverging Diamond? • Theoretical safety benefit from reduction in Theoretical safety benefit from reduction in potential vehicle-vehicle conflict points potential vehicle-vehicle conflict points •DDI: 14 Conflict Points DDI: 14 Conflict Points •Traditional Diamond Interchange: Traditional Diamond Interchange: 26 Conflict 26 Conflict Points Points •Single Point Urban Single Point Urban Interc Interchange: hange: 18 Conflict 18 Conflict Points Points
Why a Why a Diverging Diamond? Diverging Diamond? • Theoretical pedestrian safety Theoretical pedestrian safety improveme improvement with multi- t with multi- stage crossing as pede stage crossing as pedestrians strians only cross one direction of only cross one direction of traffic traffic at a time at a time • Curvature reduces vehicle speeds through Curvature reduces vehicle speeds through intersections intersections • Potential for reduction of infrastructure costs Potential for reduction of infrastructure costs through reduction of neede through reduction of needed lanes and lanes and underpass/overpass bridge width underpass/overpass bridge width
MoDOT Proposes DDI MoDOT Proposes DDI • I-435 & I-435 & Front Street Front Street Kansas City, MO Kansas City, MO – Gateway to Northeast Gateway to Northeast Industrial District Industrial District
I-435 & Front Street Alternatives I-435 & Front Street Alternatives TUDI vs. DDI TUDI vs. DDI • Estimated Costs Estimated Costs TUDI TUDI DDI DDI Con Construction truction $ 6, $ 6,866,000 866,000 $ 4, $ 4,918,000 918,000 Ri Right of Way ght of Way $ 3, 3,868,000 868,000 $ 1, $ 1,445,000 445,000 Ut Utilities lities $ 600,000 600,000 $ $ 39 391,000 1,000 Tot Total Cost l Costs $11,354,000 11,354,000 $ 6, $ 6,754,000 754,000 • Operations Operations – TUDI – TUDI – 8 lanes, LOS C-F, Capacity @ 95% lanes, LOS C-F, Capacity @ 95% – DDI – DDI – 4 lanes, LOS A-C, Capacity @ 60% 4 lanes, LOS A-C, Capacity @ 60% • Safety Safety – TUDI – TUDI – 45 Conflict Points 5 Conflict Points – DDI – DDI – 21 Conflict Points 21 Conflict Points
Why Not Select a Diverging Why Not Select a Diverging Diamond? Diamond? • The DDI is The DDI is a a new conce new concept to drivers in pt to drivers in the US the US • The crossover maneuver is not The crossover maneuver is not intuitive because intuitive because drivers travel on the drivers travel on the opposite side of the road opposite side of the road • Concern that driver unfamiliarity will Concern that driver unfamiliarity will result in an increase in crashes result in an increase in crashes
The Crossover Design The Crossover Design •Design of I-435 & Front Street Design of I-435 & Front Street DDI DDI Crossover with larger radii to Crossover with larger radii to accommodate high truck/heavy accommodate high truck/heavy vehicle % vehicle % •More typical design radii More typical design radii values expected for values expected for an an urban urban DDI Crossover DDI Crossover
FHWA Human Factors Driver FHWA Human Factors Driver Simulation Study Simulation Study • Simulation of I-435 & Front Simulation of I-435 & Front Street DDI in Highway Driving Street DDI in Highway Driving Simulator at Turne Simulator at Turner-Fairbank -Fairbank Highway Research Center Highway Research Center • Three simulated interchanges – Three simulated interchanges – DDI, DDI (Mod), and Diamond DDI, DDI (Mod), and Diamond • 74 Drivers (Balance male/female 74 Drivers (Balance male/female & over/unde & over/under 65) 65) • Results published in Results published in FHWA Tech FHWA Tech Brief (www.tfhrc.gov) Brief (www.tfhrc.gov)
I-435 & Front Street DDI Simulation I-435 & Front Street DDI Simulation
I-435 & Front Street DDI Simulation I-435 & Front Street DDI Simulation
Study MOEs and Results Study MOEs and Results • Wrong-way Violations Wrong-way Violations – No violations at No violations at crossover (1041 opportunities) crossover (1041 opportunities) • Navigation Errors Navigation Errors – Incorrect path Incorrect path on only 2.3% of opportunities on only 2.3% of opportunities • Red-light Violations Red-light Violations – Similar frequency although rare, but Similar frequency although rare, but more violation more violation opportunities with conventional diamond opportunities with conventional diamond • Speed @ Crossovers/Intersections Speed @ Crossovers/Intersections – DDI DDI – avg. 24 mph vg. 24 mph – Diamond – Diamond – avg. 34 mph avg. 34 mph
DDI Conclusions/Recommendations DDI Conclusions/Recommendations • The safety benefit combine The safety benefit combined with predicted with predicted operation operational benefits and reduced roadway width l benefits and reduced roadway width requirements make the DDI an attractive requirements make the DDI an attractive interchange alternative interchange alternative • Simulation study suggests potential driver Simulation study suggests potential driver confusion not as significant of a confusion not as significant of a concern and is concern and is mitigated with proper design (reverse curvature), mitigated with proper design (reverse curvature), signing, and markings signing, and markings
DDIs Under Consideration DDIs Under Consideration • Status of DDIs in the following states: Status of DDIs in the following states: Studied Studied Constructed Constructed In Construction In Construction
I-15 & American Fork in I-15 & American Fork in Sarasota Springs, UT Sarasota Springs, UT Under Under Construction – Construction – Project is 25% Complete roject is 25% Complete
MoDOT & DDIs MoDOT & DDIs • June 21, 2009 the first DDI in the United States June 21, 2009 the first DDI in the United States opened at I-44 & opened at I-44 & Route 13 in Springfield, MO Route 13 in Springfield, MO • I-435 & I-435 & Front Street in Kansas City, MO to be Front Street in Kansas City, MO to be constructed soon constructed soon • Planne Planned: d: – US 65 & Chestnut Expressway in Springfield, MO US 65 & Chestnut Expressway in Springfield, MO – US 60 & National Avenue in Springfield, MO US 60 & National Avenue in Springfield, MO – Botts Road & Route 150 in Kansas City, MO Botts Road & Route 150 in Kansas City, MO – I-270 & Dorsett Road in St. Louis County, MO I-270 & Dorsett Road in St. Louis County, MO
Recommend
More recommend
