What Are the Real Costs of Inspecting a Bridge Deck? Comparing Chain Drag, GPR/IRT Vehicles, and UAS with Infrared Thermography
When it comes to inspecting bridge decks, the method you choose doesn’t just affect the data quality—it significantly impacts cost, traffic disruption, and worker safety. Let’s break down the economics of three common approaches: conventional chain drag with lane closures, vehicle-mounted Ground Penetrating Radar (GPR) and Infrared Thermography (IRT) with rolling closures, and the new kid on the block—Unmanned Aerial Systems (UAS) using Infrared Thermography.
Baseline Assumption
An average bridge deck size of 17,000 sq ft is used as our basis for comparison.
MPT averages $10,000 per bridge deck of average sq ft.
Rolling closure MPT averages $4000 per bridge deck of average sq ft.
Shape
1. Chain Drag with Full or Partial Lane Closures1,2
Inspection Speed: ~6,000 sq ft per day (about 3 days per bridge)
Labor & Equipment Cost: ~$2,000/day
Maintenance and Protection of Traffic (MPT): $8,000–$12,000 total (flaggers, signs, lane closures)
Total Cost Estimate:
$6,000 (labor/equipment over 3 days)
$10,000 (avg. MPT)
Total: $16,000 per bridge
Cost per square foot: ~$0.94
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2. Vehicle-Mounted GPR and/or IRT with Rolling Closures2,3
Inspection Speed: ~17,000 sq ft per day (1 bridge/day)
Labor & Equipment Cost: ~$3,500/day
MPT (rolling closures): ~$3,000–$5,000 (escorts, traffic control)
Total Cost Estimate:
$3,500 (labor/equipment)
$4,000 (avg. MPT)
Total: $7,500 per bridge
Cost per square foot: ~$0.44
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3. UAS with Infrared Thermography
Inspection Speed: 3 bridges per day (~51,000 sq ft/day)
Monthly System Lease: $6,000 → $300/day (based on 20 working days/month)
Labor Cost: ~$1,200/day for a two-person crew
MPT: None required
Total Daily Operating Cost:
$300 (system) + $1,200 (labor) = $1,500/day
Per bridge: $500
Cost per square foot: ~$0.03
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The Bottom Line: Cost per Square Foot Comparison
Method
Total Cost/Bridge
Cost per Sq Ft
MPT Required
Workers on Bridge?
Chain Drag
$16,000
$0.94
Yes
Yes
GPR/IRT Vehicle
$7,500
$0.44
Yes (rolling)
Yes
UAS with Infrared Thermography
$500
$0.03
No
No
Shape
Conclusion: A Safer, Cheaper Future
UAS-based inspections using infrared thermography are rapidly proving their value—not only in cost savings but also in safety and efficiency. With zero lane closures, minimal disruption, and a cost per square foot that’s 30x less than chain drag, it’s a method that deserves a closer look—especially when you’re managing large inspection programs with limited budgets and potentially limited inspection seasons due to extreme weather.
