US 281 New Mainlanes + Frontage Roads

The project upgraded the existing divided facility to interstate standards by constructing new four-lane mainlanes with auxiliary lanes, converting the existing mainlanes to frontage roads, designing two new frontage road bridges, and adding new ramps on an accelerated 11-month schedule.

The project required complex bridge geometry, including a 1.1-mile divided mainlane bridge spanning two county roads and a skewed creek through a floodplain diversion channel between creeks. PGAL in-house bridge team designed all 155 spans of varying bent and beam configurations to avoid poor soils, utilities, and environmentally sensitive areas—balancing span lengths for constructability and cost efficiency. Additional geometric refinements were made to resolve a sight distance issue at a mainlane curve and superelevating ramp bridges.

To mitigate floodplain impacts, PGAL elevated 3.2 miles of new mainlanes over a FEMA Zone AE floodplain diversion channel that connected two creeks. The design included two new frontage road bridges and maintained floodplain continuity without requiring USACE permitting. PGAL’s roadway and drainage teams collaborated to develop optimized floodplain earthwork cross sections, achieving significant reductions in cut/fill while preserving hydraulic performance and avoiding new ROW acquisition.

This project marked the district’s first use of Bentley’s OpenBridge Modeler (OBM) for full bridge production with PGAL leading the design using the new platform. Working closely with TxDOT and the adjacent consultant, PGAL demonstrated its capabilities, limitations and workarounds, to help the district establish effective workflows for future project successes.