21 National Bridge Inventory. All highway bridges in the United States are inspected periodically for structural deficiency by the Federal Highway Administration (FHWA).

Data from the FHWA inspections are compiled into the National Bridge Inventory (NBI). Several of the nearly 100 variables maintained by the NBI are listed next.

Classify each variable as quantitative or qualitative.

a. Length of maximum span (feet)

b. Number of vehicle lanes

c. Toll bridge (yes or no)

d. Average daily traffic

e. Condition of deck (good, fair, or poor)

f. Bypass or detour length (miles)

g. Type of route (interstate, U.S., state, county, or city)