MDX’s Divergent Diamond Interchange – easier done than said

It’s about time to take a drive on the new DDI. On Aug. 13, the new Divergent Diamond Interchange at 27^th Avenue opens for use by commuters entering and exiting the SR 836/Dolphin Expressway.

This new, modern interchange is geared to not only improve the flow of traffic on the highway, but will significantly reduce congestion on 27^th Avenue.

In the DDI, drivers will cross to the left – or the opposite side of the road – as they pass under the expressway overpass. It is important that drivers follow the traffic signals, directional signage, and pavement markings while passing through the interchange. Negotiating the pattern will be different, but certainly easy to do – by simply following the traffic signals and pavement markings.

Despite recent comments on social media critical of Miami drivers, and questioning their ability to understand such a different-looking traffic pattern, getting through the DDI is not complicated.

There’s even been comparisons made to the road rules that Great British observes, where drivers use the left side of the road, opposite to our driving pattern. But the truth is, there are no decisions that a driver using the DDI has to make, other than simply “follow the road.” That’s because it is the road itself that moves left and then to the right again – so drivers just need to stay within the lines.

To see how this really works, drivers are encouraged to view DDI simulation videos on the MDX website.

The DDI’s greatest benefit is that it eliminates the existing conflicts that currently exist at expressway on and off ramps that create weaving and uncertainty, and which contribute to traffic congestion. This modern new design facilitates large volumes of traffic entering and exiting the expressways to improve traffic flow on the local streets. The new configuration also facilitates U-turns for motorists who take the wrong exit and need to return to the expressway. 

Presently, there are 89 DDI’s in the U.S., and their use is growing. That’s because they are proven way to increase safety and to reduce backs ups. In fact, in Springfield, Mo., where one of the first DDIs was introduced, there has been a 60 percent drop in accidents.

The primary message MDX is promoting in its recent educational campaign regarding the 27^th Ave. interchange is to: keep alert, follow the markings on the road, and pay attention to the signs. Later this fall, a second DDI will open, on 57^th Avenue.

All these improvements are part of the modernization of SR 836, the Dolphin Expressway from 57^th to 17^th Avenues – the most congested segment of the Dolphin. MDX is literally demolishing portions of a 55-year-old expressway and constructing a modern multimodal expressway to serve 3 million residents and 16 million annual visitors. They are accomplishing this while moving thousands of commuters and commerce to Miami-Dade’s most important economic engines such as the Miami International Airport (MIA) and other high-employment areas.

One of the biggest changes will be the exit to MIA, which is now will be accessed from the right, whereby eliminating the weaving created by drivers trying to reach the existing left-side exit. This new ramp is expected to open also this fall. The exit from the airport to westbound Dolphin has already been completed.

All improvements on the Dolphin, including the reconstruction of the 87^th Avenue interchange, use a system of collectors and distributors roads to create safer and faster access to the exits and entrances to the expressway. This eliminates competing movements with those using the general through-lanes to allow them to move faster without conflicts.

Expressways simply cannot be continually expanded to keep up with the demand of a growing community, so there are other operational improvements and modifications that must be sought out. The old-style cloverleaf interchanges, featuring large round ramps, no longer work for the many users of high volume expressways. Innovative designs such as the Divergent Diamond Interchange are the answer.

There are also choices on the books that will be offered as part of MDX’s transit initiatives. They include adding special lanes on the Dolphin called “XT lanes” or “Xpress Technology Lanes.” These brick-colored lanes on the inner shoulders of the expressway will carry a new express-bus service operated and financed by MDX to attract drivers who use their cars today but would like to see alternative means of traveling around town.

The idea is to offer choices in order to move more people. This service will initiate from the Dolphin Station Park and Ride west of the Turnpike and NW 12^th Street, which is nearing completion, to downtown Miami and likely to the airport. Service would start upon completion of the improvements on SR 836.

Coming soon, stay tuned for news of a new multimodal Dolphin Expressway to serve the commerce and commuting needs of Miami-Dade County well into the new millennium.

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