The Maritime Off-Ramp at the intersection of I-80 and I-880 in Oakland, North America's first curved welded steel orthogonal isotropic bridge, provides access to the Port of Oakland through a U-turn from westbound I-80. The ramp is 2,356 ft long and has a 250-ft radius horseshoe shape. The California Department of Transportation (Caltrans) chose steel bridges to minimize traffic delays during bridge erection. Designers selected a closed cell structure for the horseshoe shape of the bridge as the most economical shape to resist torsional forces. The substructure includes reinforced concrete "T" bents with a single column with spiral reinforcing ties. Two special bearings connect the superstructure to each "T" bent.

The contractor fabricated 13 full-bridge-width orthogonal isotropic sections 7 ft 0 in deep by 35 ft 6 in wide up to 37 ft 6 in wide, with lengths ranging from 123 to 219 ft per section. All sections shipped with a steel orthogonal isotropic deck and with installed steel barrier rails. All fabricated steel totaled 5,014 tons.

Installation included special heavy-lift hydraulic platforms to move the bridge sections. Each of the 13 bridge sections was moved three times: from the fabrication facility to the barge, from the barge to the staging area beside the freeway, and from the staging area into its final location. The sections were staged on the east side of the freeway and crossed over during night erection during a 10-hr window beginning at midnight on a Saturday. The contractor faced stiff fines for each minute exceeding the time limit. Installation of three of the sections required closing half of the freeway lanes, below which approximately 500,000 vehicles cross per day. The segment over the westbound lanes was erected around midnight on one Saturday night, and the segment over the eastbound lanes was erected the following Saturday night.

Unique seismic detailing includes use of rubber dock fenders as seismic shock absorbers to reduce forces between completed bridge sections. Poly-tetra-fluoro-ethylene (PTFE) spherical bearings allow for rotation and expansion of members and can resist high lateral forces, including seismic forces. A central shear key provides additional lateral capacity.