Do Steel Bridges Age Worse Than Concrete? Superstructure Condition by Age for 58,984 Spans in the 2025 National Bridge Inventory of Ohio, New York and Pennsylvania

Using 2025 NBI on-records for Ohio, New York and Pennsylvania, I compare superstructure condition ratings (item 59) for steel (kinds 3-4), concrete (1-2) and prestressed (5-6) bridges by age. Among 58,984 spans built 1900-2024, steel and concrete have similar mean ages (57.7 and 59.3 years) and mean ratings (6.59 and 6.49); prestressed bridges are younger (38.5 years) and healthier (mean 7.12). The raw steel-concrete mean gap is only +0.10 rating points. Within ten-year age bins the gap stays between -0.05 and +0.22. OLS slopes of rating on age are -0.025 per year for steel and -0.030 for concrete. A logit for poor condition (rating ≤4) gives an average marginal effect of 0.29 points per year of age and +8.9 points for steel versus concrete, with a negative age-steel interaction: steel's disadvantage is larger at young ages and shrinks as both materials deteriorate. Poor-condition shares are 6.9% (steel), 6.1% (concrete) and 3.1% (prestressed).