Gateway Expressway And I-275 Interchange Design-Build — Pinellas County, FL
Client
- Florida Department of Transportation District 7
Project Value 
$545 Million
Market
Transportation
Services
Alternative Project Delivery
We served as the Lead Designer and Team Manager for the Gateway Expressway and I-275 Interchange, delivering comprehensive multidisciplinary design services for this transformational project in East Pinellas County. From the start, we guided coordination across roadway, structural, and ITS elements to improve regional mobility. As a result, the project established direct express connections between key corridors.
Our Role As Lead Designer
Throughout the Gateway Expressway and I-275 Interchange, we provided integrated design services for structures, roadway, drainage, ITS, signalization, and signing and pavement markings. Ultimately, our leadership ensured a coordinated design that delivered lasting mobility benefits for the region.
SR 690 Expressway Design And Construction
First, we designed SR 690, a new four‑lane static toll expressway connecting US 19 to west of I‑275. This work formed a critical part of the Gateway Expressway and I-275 Interchange and supported efficient east‑west travel.
Key design features included:
- Flyovers connecting to mainline US 19
- Structures over crossroads and environmentally sensitive areas
- Viaducts, ramps, and structure widenings
Additionally, we rehabilitated existing bridges to extend service life and enhance safety.
SR 686A Elevated Expressway And Local Improvements
Next, we delivered design services for SR 686A, a four‑lane elevated toll expressway from the Bayside Bridge to I‑275. The alignment runs within the Roosevelt Boulevard median and includes a new interchange at SR 688. Subsequently, the roadway continues south on a new alignment before merging with SR 690 via flyover bridges.
Supporting improvements included:
- Reconstruction of SR 686 as two one‑way surface roads
- New access roads for St. Pete‑Clearwater International Airport
- Resurfacing of 118th Avenue North
- Utility coordination with Largo, Pinellas Park, and Pinellas County
I-275 Express Lanes Integration
The third component expanded dynamic toll express lanes along I‑275, from south of Gandy Boulevard to north of 4th Street North. Consequently, the Gateway Expressway and I-275 Interchange now provides direct express connections between I‑275 and the Gateway corridors.
Major Structural Features
We designed 32 bridge structures that balanced constructability with long‑term performance.
Highlights included:
- 24 new bridges, five widenings, and three modifications
- Florida‑I Beam bridges with spans from 90 to 200 feet
- A 4,035‑foot viaduct with post‑tensioned hammerhead pier caps
- Curved steel flyovers with spans up to 320 feet
Notably, we used SPMTs to remove the existing 4th Street flyover, which minimized traffic impacts.
