State decided not to go with the diverging diamond design used at the interstate exit at University Parkway.

MANATEE COUNTY — Construction is underway on an $80.8 million redesign of the Interstate 75 and State Road 70 interchange that, weather permitting, is likely to be completed by fall 2021.

The Florida Department of Transportation chose not to use a diverging diamond as it did when rebuilding the interchange at University Parkway and I-75.

Diverging diamonds are appropriate for interchanges with “a heavy volume of left-hand turns,” Brian Bollas, strategic education and outreach manager for the FDOT, said. “Diverging diamonds are not appropriate for every single interchange.”

Instead, contractor Sacyr Construction USA will convert what is now a “modified cloverleaf” interchange into a “modified diamond” design. The changes are intended to make the crossroads more efficient.

When the interchange is completed, drivers will discover some variations in how they enter and exit either I-75 or S.R. 70 depending on which direction they are headed.

Southbound on I-75 to west on S.R. 70: Use the exit ramp in the northwest quadrant of the interchange and go to the signalized intersection as drivers do now.

Southbound on I-75 to east on S.R. 70: Use the exit ramp in the northwest quadrant and go to the signalized intersection as drivers do now.

Northbound on I-75 to west on S.R. 70: Use the exit ramp in the southeast quadrant and go to the new signalized intersection. The current looped ramp in the northeast quadrant that drivers use to merge into the westbound lanes of S.R. 70 will be eliminated.

Northbound on I-75 to east on S.R. 70: Use the exit ramp and go to the new signalized intersection. The current exit ramp, which merges with eastbound traffic and has no signal, will be eliminated.

Eastbound on S.R. 70 to north on I-75: Go to the new signalized intersection east of the interchange and turn left.

Eastbound on S.R. 70 to south on I-75: Use the entry ramp in the southwest quadrant of the interchange as drivers do now.

Westbound on S.R. 70 to north on I-75: Use the entry ramp as drivers do now.

Westbound on S.R. 70 to south on I-75: Get in the right lane and take the new looped ramp in the northwest quadrant of the interchange.

Emergency stopping sites will be added to the exit ramps.

The project also involves widening I-75 from north of University Parkway to south of State Road 64 from three lanes in each direction to four. The addition will be an “auxiliary” lane intended for traffic going from one interchange to the next, leaving the remaining lanes for drivers going greater distances.

The overpass at S.R. 70 and a bridge over the Braden River will be widened.

S.R. 70 will be resurfaced from Tara Boulevard to 87th Street East and include 5-foot-wide sidewalks and 6.5-foot bicycle lanes.

Noise walls are to be built for these subdivisions flanking I-75: Creekside (early 2019), Tara Preserve (early 2019), River Place (mid 2019) and Willowbrook (early 2020).