Questions and Answers on the National Bridge Inspection Standards, 23 CFR Part 650, Subpart C
Except for any cited statutes or regulations, the contents of these Q&As do not have the force and effect of law and are not meant to bind the public in any way. These Q&As are intended only to provide information regarding existing requirements under the law or agency policies.
650.311 Inspection interval
Q311-1 Why are there two (2) methods for determining the interval of bridge inspections? (New 3/01/2023)
A311-1 Allowing two (2) methods provides State transportation departments, Federal agencies, and Tribal governments flexibility in how they consider risk in their bridge inventories. Method 1 offers a simplified assessment approach, while Method 2 offers a more rigorous assessment methodology, to determine inspection intervals. The methods for establishing risk-based intervals are based on the NCHRP Report 782 Proposed Guideline for Reliability Based Bridge Inspection Practices1 and FHWA's practice prior to this final rule for establishing 48-month inspection intervals.
Q311-2 How do State transportation departments, Federal agencies or Tribal governments use Method 1 and Method 2 to set inspection intervals on bridges in their inventory? (New 3/01/2023)
A311-2 FHWA published a memo outlining the criteria and process for State transportation departments, Federal agencies, and Tribal governments to follow as they develop inspection interval policies that fulfill the requirements of 23 CFR 650.311. The memo can be obtained at: https://www.fhwa.dot.gov/bridge/pubs/memo_inspection_interval_guidance.pdf
Q311-3 Why is there a bridge inspection interval tolerance? (New 3/01/2023)
A311-3 FHWA recognizes severe weather, bridge inspector safety, inspection quality, resource optimization, or other unique situations may be a reason to adjust the scheduled inspection date.
In these situations, the adjusted inspection date must 1) not extend more than two (2) months after the month the inspection was due for any inspection interval less than 24 months and 2) not extend more than three (3) months after the month the inspection was due for any inspection interval 24 months or greater (23 CFR 650.311(e)(1)-(2)).
Inspection interval tolerances are intended to provide some flexibility. When tolerances are applied, the longest time period allowed between inspections is the applicable interval plus the allowed tolerance. For example, a routine inspection on a 12-month interval could be performed during the 14th month if the tolerance is applied. Repeatedly applying the tolerance to the next inspection will create inspection date creep and may impact an owner’s ability to perform future inspections in a timely manner due to other limitations (e.g., available resources, inspection workload, schedule, seasonal/weather conditions, etc.).
Q311-4 What if an inspection cannot be performed within the accepted tolerance? (New 3/01/2023)
A311-4 Exceptions to inspection interval tolerances due to rare and unusual circumstances must be approved by FHWA in advance of the inspection due date, plus the tolerance (23 CFR 650.311(e)(3)). For example, if an inspection with an interval of 24 months is due on June 17, 2022, an exception request must be approved by FHWA before the end of the 3-month tolerance (i.e., September 30, 2022). However, a request for exception should be made when the potential for not meeting the tolerance becomes known to provide FHWA with adequate time for review and approval.
1The NCHRP Report 782 may be found at the following URL: http://www.trb.org/Publications/Blurbs/171448.aspx