95% cost reduction across an 11,000-bridge inspection network

The challenge

Michigan DOT is responsible for over 11,000 bridges and structures statewide, each requiring periodic inspection under federal NBIS standards. Conventional inspection methods rely on snooper trucks, under-bridge inspection vehicles, and rope-access teams — costing an average of $4,600 per structure. Each inspection also requires lane closures, traffic control plans, and multi-day crew mobilization, creating significant disruption on high-traffic corridors.

The approach

The solution

Drone inspections captured high-resolution imagery of bridge decks, undersides, piers, and abutments. Pilots flew planned grid patterns around each structure, collecting overlapping photos for 3D reconstruction. Thermal sensors identified delamination and moisture intrusion invisible to the naked eye. Reports were formatted to align with existing NBI condition-rating workflows, allowing inspectors to integrate drone data without changing their assessment process.

The results

Drone inspection cost averaged $250 per structure — a 95% reduction from the $4,600 conventional baseline. Single-day turnaround replaced the 6–8 day cycle required for snooper-truck mobilization, crew scheduling, and traffic control. Zero lane closures were needed, eliminating traffic disruption and associated liability exposure.

At scale, applying drone inspection across even 20% of Michigan’s 11,000-structure network would represent over $9.5 million in annual inspection cost savings — while producing higher-resolution visual records that enable longitudinal change detection across inspection cycles.