MUTCD Interim Approvals and Official Interpretations: What Traffic Control Contractors Should Know

The MUTCD is a printed standard, but the rules around traffic control devices do not freeze between editions. New devices get tested, odd field situations come up, and the Federal Highway Administration has two tools for handling them without waiting for a full rewrite: interim approvals and official interpretations. If you plan, price or set up work zones, you will eventually see one cited in a plan note, a spec or an agency email.

This post explains what each tool is, how they differ, and how to treat them in practice. It is general information about how the process works. Requirements vary by state, county and city, so verify what applies to your project with the authority having jurisdiction. Nothing here is a legal interpretation of whether a specific device is allowed on your job.

Where these fit in the bigger picture

The manual itself changes through Federal Register rulemaking. FHWA's amendment process page explains that since FHWA took over updating the MUTCD in 1979, changes go through notices in the Federal Register, and that changes come out of research, experimentation and practical experience, including work by the Traffic Control Devices Pooled Fund Study. That path is slow by design. Interim approvals and interpretations sit alongside it.

If you are not sure where to read the manual or which edition is current, start with our guide to finding the official MUTCD online.

Interim approvals: trying a device before it is in the manual

FHWA's interim approvals page says Section 1B.07 of the 11th Edition gives FHWA the authority to issue them. In FHWA's words, such approvals allow interim use, pending official rulemaking, of a new traffic control device, a revision to the application or manner of use of an existing device, or a provision not specifically described in the MUTCD.

Key points from that page:

• They are based on evidence. FHWA says interim approvals are considered on the results of successful experimentation, studies or research, and an intention to place the new or revised device into a future rulemaking.
• The agency asks, not the vendor. A jurisdiction that wants to use the device submits a written request to the director of FHWA's Office of Transportation Operations. The request has to say whether blanket jurisdiction-wide approval is sought or name the locations, and must include the jurisdiction's agreement to comply with certain conditions in paragraph 10 of Section 1B.07.
• A state can ask for all its jurisdictions. FHWA says a state may request an interim approval covering every jurisdiction in that state.
• There is a current list. FHWA lists current interim approvals valid under the 11th Edition. At the time of writing, the page shows IA-23, an optional-use approval for a residential driveway temporary signal dated January 8, 2025.
• Some end. FHWA also lists terminated interim approvals issued under the 2009 manual for devices that were later incorporated, in whole or in part, into the 11th Edition. FHWA says agencies that installed devices under those approvals should consult the 11th Edition sections and revise installations as needed to comply.

For a contractor, the main lesson is that an interim approval is tied to the agency that holds it. If a spec or plan note references one, the permission belongs to that jurisdiction, under the conditions in its approval. It does not mean the device is acceptable on a different agency's road. Ask the owner of the road for the approval document and any conditions, and keep a copy with the job file.

Official interpretations: how FHWA reads the manual

An interpretation answers a different question. FHWA's official interpretations page says they are issued when unique situations arise for device applications that might need interpretation or clarification. An interpretation can cover the application and operation of standard devices, the official meaning of standard devices, or variations from standard designs.

Who can ask: FHWA states that any jurisdiction, company or individual may send a written request to the director of the Office of Transportation Operations. The request should include a concise statement of what interpretation is sought, a description of the condition that prompted it, any helpful illustration and any supporting research data. FHWA replies in writing.

The legal status is the part people misread. According to FHWA's page:

• Until formal rulemaking revises the manual, an interpretation should be considered FHWA policy guidance, or FHWA's recommendation of appropriate or best practice.
• Agencies are encouraged to follow it for new designs or projects, but there is no legal requirement to do so.
• Interpretations create no requirement to modify or replace existing devices in the field. Compliance dates for that are set along with rulemakings.
• Some interpretations clarify that a device design or application meets the intent of the MUTCD, even though the text does not say so. In that case agencies may use or continue using it at their option, but only in the manner the interpretation specifies.

After an interpretation is issued, FHWA says it considers proposing text changes for a future rulemaking, so a recurring question can eventually become clearer manual text.

Side by side

	Interim approval	Official interpretation
What it does	Permits interim use of a new or revised device or application	Clarifies how FHWA reads existing MUTCD provisions
Who requests	A jurisdiction, or a state for all jurisdictions	Any jurisdiction, company or individual
Binding force	Permission granted to the requesting agency, with conditions	Policy guidance; no legal requirement to follow
Outcome	Intended to feed future rulemaking	May lead to proposed text changes in future rulemaking

How to handle them on a job

When a plan or spec cites one, get the document. Ask the project engineer for the approval memo or interpretation letter. A plan note that says "per FHWA" is not enough for a crew lead to act on.

Do not assume it travels. An approval to one agency does not automatically apply on the next road owner's project. A device the crew used last week under one agency's approval may not be accepted this week by another.

Do not treat an interpretation as a loophole. An interpretation that says a design meets the intent of the manual permits use in the manner the interpretation specifies, and only that. If your setup differs, you are outside it.

Record it on the ticket. If a nonstandard device or arrangement was used under an approval, note the approval number or reference in the job record and the daily ticket so a later audit or dispute has the answer in one place.

Route questions through the agency. If your crew believes a plan conflicts with the manual, the right move is to raise it with the agency's engineer and, where the plan is changed in the field, document the change. Our guide to field changes to an approved traffic control plan covers that workflow.

Keep the references with the job

Interim approvals and interpretations are exactly the sort of paperwork that gets lost in an email thread. Traffic OS keeps job records, GPS-stamped signed daily tickets and equipment history together, so a note about what was set up and under what reference stays attached to the work. See features, flat-tier pricing with no per-user charge, the comparison with ServiceTitan, or book a demo. For how the manual intersects with permits, read MUTCD compliance and traffic control permits.