Diverging diamond interchange – Wikipedia

2023-04-15 13:44:27

Freeway interchange design

A diagram illustrating visitors actions within the interchange

A diverging diamond interchange (DDI), additionally referred to as a double crossover diamond interchange (DCD),^[1]^[2] is a subset of diamond interchange through which the opposing instructions of journey on the non-freeway highway cross one another on both facet of the interchange in order that visitors crossing the freeway on the overpass or underpass is working on the other driving side from that which is customary for the jurisdiction.^[2] The crossovers might make use of one-side overpasses or be at-grade and managed by traffic light.

The diverging diamond interchange has benefits in each effectivity and security, and—regardless of having been in use in France because the Nineteen Seventies—was cited by Popular Science as top-of-the-line engineering improvements of 2009^[3] and within the U.S. has been promoted as a part of the Federal Freeway Administration’s Every Day Counts initiative.^[4] The stream by way of a diverging diamond interchange utilizing overpasses on the crossovers is restricted solely by weaving, and the stream by way of an implementation utilizing visitors lights is topic to solely two clearance intervals (the time throughout which all lights are crimson in order that the intersection might absolutely clear) per cycle.^[5]^[6]

The best security concern of the interchange stems from its relative rarity, as drivers instinctively attempting to remain on the customary facet of the highway may use the crossover intersections to show towards the posted route of journey. It is a uncommon prevalence; it’s doable solely when visitors is so sparse that no automobiles from the oncoming route are stopped on the mild, and clear signage additional reduces the chance of such errors.^{[citation needed]}

Historical past[edit]

Footage from the primary diverging diamond interchange in the US, in Springfield, Missouri
High left: Visitors enters the interchange alongside Missouri Route 13
High proper: Visitors crosses over to the left facet of the highway
Backside left: Visitors crosses over Interstate 44
Backside proper:Visitors crosses again over to the appropriate facet of the highway.

Lunchtime visitors on the diverging diamond interchange on the James River Freeway and Route 13 in Springfield

The primary identified diverging diamond interchanges had been in France within the communities of Versailles (A13 at D182), Le Perreux-sur-Marne (A4 at N486) and Seclin (A1 at D549), all constructed within the Nineteen Seventies.^[7] The ramps of the primary two have since been reconfigured to accommodate ramps of different interchanges, however they proceed to operate as diverging diamond interchanges. The interchange in Seclin (at 50°32′41″N 3°3′21″E / 50.54472°N 3.05583°E / 50.54472; 3.05583) between the A1 and Route d’Avelin was considerably extra specialised than within the diagram at proper: eastbound visitors on Route d’Avelin meaning to enter the A1 northbound should preserve left and cross the northernmost bridge earlier than turning left to proceed north onto A1; eastbound visitors persevering with east on Route d’Avelin should choose a single middle lane, merge with A1 visitors that’s exiting to proceed east, and cross a middle bridge. All westbound visitors that’s persevering with west or turning south onto A1 makes use of the southernmost bridge.

In the US in 2005, the Ohio Department of Transportation (ODOT) thought-about reconfiguring the present interchange on Interstate 75 at U.S. Route 224 and State Route 15 west of Findlay as a diverging diamond interchange to enhance visitors stream. Had it been constructed, it might have been the primary DDI in the US.^[8] By 2006, ODOT had reconsidered, as a substitute including lanes to the present overpass.^[9]^[10]

Southbound method to the I-44/Route 13 interchange in Springfield

The Missouri Department of Transportation was the primary US company to assemble one, in Springfield on the junction between I-44 and Missouri Route 13 (at 37°15′01″N 93°18′39″W / 37.2503°N 93.3107°W / 37.2503; -93.3107). Building started the week of January 12, 2009, and the interchange opened on June 21, 2009.^[11]^[12] This interchange was a conversion of an current customary diamond interchange, and used the present bridge.^[13]

In 2010, the Federal Highway Administration launched a publication titled “Different Intersections/Interchanges: Informational Report (AIIR)”^[14] with a chapter devoted to this design. Extra analysis was carried out by a partnership of the Virginia Polytechnic Institute and State University and the Turner-Fairbank Highway Research Center and printed by Ohio Part of the Institute of Transportation Engineers.^[15]

On August 14, 2011, the Kentucky Transportation Cabinet (KYTC) accomplished conversion of the intersection of U.S. Route 68 and Kentucky Route 4 in Lexington to a diverging diamond design, the primary within the state and the sixth accomplished nationally.^[16] Stantec, the engineers who accomplished the upgrades to the interchange, famous the answer whereas offering substantial price financial savings over different doable choices additionally has decreased accidents by 45 %, improved visitors stream to greater than 35,000 autos per day, and included KYTC’s aim to offer new paths for bicycles and pedestrians by way of the realm.^[17] That very same day in Highland, Utah the seventh U.S. diverging diamond interchange opened on the intersection of I-15 and Timpanogos Freeway.^[18] In keeping with the U.S. Department of Transportation the targets of this intersection improve had been related, growing visitors capability and improved pedestrian and bicycle entry whereas reaching these targets with out requiring substantial revisions to the present interstate overpass. Quoting a June 2014 USDOT publication, “…the DDI has made journey extra environment friendly and accessible for all customers.”^[19]

2016 noticed the introduction of diverging diamond interchages to 3 states. In February, the Oregon Department of Transportation opened one in Phoenix.^[20]^[21] In October, the New Mexico Department of Transportation transformed the crossing of NM 14 (Cerrillos Road) and Interstate 25 in Santa Fe.^[22] In November, the Delaware Department of Transportation accomplished the conversion of the DE-1 and DE-72 (Wrangle Hill Rd) overpass west of Delaware City.^[23]^[24]

The primary interchange in Canada opened on August 13, 2017, at Macleod Trail and 162 Avenue South in Calgary, Alberta^[25] adopted by one in Regina, Saskatchewan the subsequent yr as a part of the Regina Bypass challenge.^[26]

The primary diverging diamond interchange in Australia opened to visitors by the Queensland Department of Transport and Main Roads on November 28, 2019. The interchange, positioned in Caloundra, Queensland, connects Caloundra Highway to the Bruce Highway. The previous interchange was upgraded and transformed as a part of the bigger Bruce Freeway Improve Program.^[27]^[28]

In December 2019, the Virginia Department of Transportation accomplished the conversion of the interchange at Courthouse Highway and I-95 in Stafford, VA right into a diverging diamond interchange.^[29]

In 2020, the California Department of Transportation (Caltrans) accomplished the primary diverging diamond interchange in California. An interchange at State Route 120 and Union Highway in Manteca, California was transformed to this interchange and opened to visitors on November 25.^[30]^[31]

Operational[edit]

As of October 14, 2022^[update], over 160 DDIs had been operational the world over together with:

3 in Australia with extra deliberate^[32]^[33]^[34]
1 in Belgium^[35]
3 in Canada^[36]
1 in Denmark opened September 17, 2017^[37]
2 in France, inbuilt Nineteen Seventies
1 in Malaysia
2 in Saudi Arabia
2 in South Africa
1 within the United Arab Emirates
1 in Costa Rica
Over 150 in the US of America with 80 extra underneath building^[38]

Benefits[edit]

Two-phase alerts with quick cycle lengths, considerably decreasing delay.^[39]
Lowered horizontal curvature reduces the chance of off-road crashes.
Will increase the capability of turning actions to and from the ramps.
Doubtlessly reduces the variety of lanes on the crossroad, minimizing area consumption.
Reduces the variety of battle factors, thus theoretically enhancing security.^[2]
Will increase the capability of an current overpass or underpass, by eradicating the necessity for flip lanes.
Prices considerably lower than a traditional interchange.^[40]

Disadvantages[edit]

Drivers might not be acquainted with configuration, significantly with regard to merging maneuvers alongside the other facet of the roadway or the crossover stream of visitors.^[41]
Pedestrian (and different sidewalk-user) entry requires at the very least 4 crosswalks (two to cross the 2 signalized lane crossover intersections, whereas two extra cross the native highway at every finish of the interchange).^[42]^[41] This may very well be mitigated by signalizing all actions, with out impacting the two-phase nature of the interchange’s alerts.
Free-flowing visitors in each instructions on the non-freeway highway is unimaginable, because the alerts can’t be inexperienced at each intersections for each instructions concurrently.
Freeway bus stops should be sited exterior the interchange.
Permitting exiting visitors to re-enter the by way of highway in the identical route requires leaving the interchange on the native highway and turning round, e.g., through a median U-turn crossover. This impacts a number of use instances:^[41]
- Drivers who take the mistaken exit
- Bypassing a crash on the bridge
- Permitting an oversize load to bypass a low bridge

Additional concerns[edit]

No requirements presently exist for this design.
The design will depend on site-specific circumstances.
Extra signage, lighting, and pavement markings are wanted past the degrees for the standard diamond interchange.
Native highway ought to be a low-speed facility, ideally underneath 45 mph (72 km/h) posted pace on the crossroad method. Nevertheless, this can be mitigated by using a better design pace for the crossing actions.

Double crossover merging interchange[edit]

3D laptop generated DCMI

DCMI visitors stream patterns

A free-flowing interchange variant, patented in 2015,^[43] has obtained current consideration.^[44]^[45]^[46] Known as the double crossover merging interchange (DCMI), it consists of components from the diverging diamond interchange, the tight diamond interchange, and the stack interchange. It eliminates the disadvantages of weaving and of merging into the skin lane from which the usual DDI variation suffers. A freeway U-turn requires weaving, nonetheless. As of 2016, no such interchanges have been constructed.