SAE J595 and J845 warning-light classes: what Class 1 means and when you need it
Written by Shmaya Krinsky, K&K Emergency Systems, Opa-locka, Florida. We build and upfit ambulances, fire apparatus and police vehicles, and we sell the parts we install. Updated October 2026.
Many of the warning lights we sell carry a line like "SAE J595 Class 1" or "SAE J845 Class 1" on the datasheet. Buyers ask us what it means, whether they need it, and whether a cheaper light that does not list it is good enough. Here is the short version, then the detail.
The short version
- SAE is SAE International, the engineering society that publishes the vehicle-lighting standards referenced by North American vehicle specifications and standards bodies such as NFPA.
- J595 covers directional flashing warning devices: lightheads, grille lights, surface mounts and similar single-direction devices for authorized emergency, maintenance and service vehicles.
- J845 covers omnidirectional and selective-coverage warning devices. Beacons are the common example, but a J845-rated device is not necessarily 360-degree; the standard has an "A" category (all-around) and an "S" category (selective coverage).
- Class 1, 2 and 3 are performance tiers defined by purpose. Class 1 is for attention-getting warning when requesting right of way or working at a hazardous or emergency scene. Class 2 is for traffic-hazard warning, such as a blocked lane or a slow-moving vehicle. Class 3 is for vehicle identification. Class 1 has the highest minimum performance.
- For ambulances, fire apparatus and police vehicles, our practice is to specify Class 1 for the warning functions, subject to the governing vehicle specification, the installed-system requirements and state law. The class on a single lighthead does not by itself make a vehicle compliant with anything.
What the SAE standards actually test
The standards define how a warning device is measured. A device is tested on a photometric bench and evaluated for the required angular distribution of light (up, down, left and right of straight ahead), peak intensity, and time-dependent output, because the measurement has to account for how the light flashes, not only how bright its peak is. The result has to meet the applicable requirements for the class claimed, in the color claimed.
Color is covered by a separate SAE standard, J578, which defines the chromaticity boundaries for signal colors including red, blue, amber and white. A red device that is bright enough can still fail if its color falls outside the J578 boundary.
Warning-light qualification also involves environmental testing, such as vibration, moisture, dust, corrosion and temperature; the August 2021 revision of J595 added an allowance for random-vibration testing. Exactly which tests apply depends on the standard, the edition and the device. A datasheet line that says "J595 Class 1" tells you the manufacturer claims the photometric class; it does not by itself prove the device passed every environmental test. Ask whether the compliance statement covers the full applicable standard or only the Class 1 photometry, and ask for the supporting test documentation.
The complete performance tables and acceptance rules are in the standards themselves, which SAE sells. We do not reprint them here, and we do not quote class ratios, because the exact figures depend on the standard, edition, color and test direction.
Class 1, Class 2, Class 3
| Class | Purpose as defined by SAE | Where it typically appears |
|---|---|---|
| Class 1 | Attention-getting warning: requesting right of way, or hazardous and emergency activity. | The tier we specify for the warning functions on ambulances, fire apparatus and police vehicles, subject to the governing specification. Check your own specification. |
| Class 2 | Traffic-hazard warning, including blocked lanes and slow-moving vehicles. | Select the class and color required by the vehicle's warning function and governing specification. As one public example, MnDOT's non-LED work-zone warning-light requirements specify SAE J1318 or J845 Class 1 or 2, yellow or amber lenses, and 360-degree coverage; its separate LED requirements call for California Title 13 compliance and inclusion on MnDOT's list. |
| Class 3 | Vehicle identification to other road users. | The lowest tier. Whether it is acceptable for a given use is set by the buyer's specification or local rules, not by the class alone. |
The vehicle type does not determine the class. The function the light performs and the specification you are building to do.
Does my vehicle need Class 1?
Which standard applies. NFPA 1901 (fire apparatus) and NFPA 1917 (ambulances) were consolidated into NFPA 1900 in the 2024 edition. The edition that governs your build is the one adopted by your authority or written into your contract, which may still be an older edition. Do not assume the newest edition applies to an existing contract.
Ambulances. NFPA 1917 references both SAE J595 and J845 for warning devices. The federal KKK-A-1822F specification, through Change Notice 14 dated July 15, 2021, replaced its lighting section 3.8.2 and specifies J845 mechanical, environmental and photometric procedures. Both documents address the emergency lighting as a system, with zones, levels, operating modes and requirements for demonstrating compliance of the installed configuration. Picking Class 1 lightheads is a sensible starting point, but compliance is established by the complete documented system, not by the class rating on each part.
Fire apparatus. NFPA 1901, now within NFPA 1900, organizes the optical warning system around zones (front, sides and rear, upper and lower) and references the SAE test standards. Our practice is Class 1 lightheads for the warning zones; that is our installation judgment, not a clause in the standard, and the installed system still has to meet the zone requirements of the governing edition.
Police and other authorized emergency vehicles. State rules vary and you should check your own state's vehicle code and administrative regulations. California is a useful example of how different they can be: California Title 13 does not use SAE Classes 1 to 3. Section 812 establishes its own warning-lamp Classes A through E, and sections 813 to 818 set performance, tests, colors and applications. Under California Vehicle Code section 26104, manufacturers must hold laboratory data showing compliance before offering covered devices for sale, and the CHP may request that data. A product marketed as "SAE Class 1" is not automatically compliant in California, and there is no California listing number to look for on the box.
Volunteer, POV and courtesy lights. A Class 1 rating does not make a light legal to run. Eligibility, permits, permitted colors, placement, visibility and when the light may operate are all set by state law. Florida Statute 316.2398, for example, sets authorization and use conditions for volunteer responders. Check your state before buying.
What to look for on a datasheet
- The exact standard and class: "SAE J595 Class 1" (directional) or "SAE J845 Class 1" (omnidirectional or selective coverage). A bare "SAE compliant" claim is not enough to verify the warning performance you need. Ask for the standard, edition, class, color and operating configuration.
- The color and pattern the rating applies to. Ratings can differ by color and configuration within one model. Federal Signal's MicroPulse Wide Angle datasheet, for example, lists different J595 classes for different colors on a dual-color head. Ask for the class per color and per approved flash pattern.
- An ingress protection rating suited to the actual exposure. Our shop practice is IP67 or better for lightheads mounted low on the body, but an IP rating is a separate question from the SAE class, and you should check a complete assembly's rating separately from its modules. Federal Signal's Allegiant lightbar, a Class 1 exterior product, is rated IP65. See our IP ratings explained post.
- Operating voltage range and current draw, which you need to size the controller, circuit protection and wiring. They are inputs, not a complete sizing method.
Products we install
Whelen and Federal Signal both publish SAE class ratings for their lightheads, and both offer Class 1 products. Not every model or color in either catalog is Class 1; Federal Signal's MicroPulse C perimeter light, for example, lists J845 Class 2 for its single-color model. Check the specific model, standard, color and pattern. Browse our emergency lighting collection, or call us at (305) 317-2619 if you need help speccing a lighting package to your governing NFPA 1900 edition or KKK-A-1822 requirement. A compliant system needs a defined configuration and supporting documentation, which we work through with you.
Frequently asked questions
Is SAE J595 the same as DOT approval? No, and nothing is "DOT approved" in the sense of a pre-approval. NHTSA does not pre-approve lamps; manufacturers self-certify compliance with FMVSS 108, the federal standard for required lighting such as headlamps, tail lamps and turn signals. SAE J595 and J845 cover warning devices. If a warning light also performs a required function (brake, tail or turn), it must meet FMVSS 108 for that function. Supplemental lighting must also not impair the required lighting, and commercial installers are subject to the federal "make inoperative" prohibition, so placement and wiring of added lights matter. NHTSA's December 13, 2024 interpretation letter on flashing amber lights is worth reading if you install on vehicles that are not authorized emergency vehicles.
Is "Class 1" the same as "Title 13"? No. Title 13 is California's own classification scheme (Classes A through E) with its own tests. An SAE Class 1 rating does not establish Title 13 compliance.
Who tests the lights? Testing can be done by the manufacturer or by a laboratory on its behalf; the KKK-A-1822F lighting provisions say so explicitly. A manufacturer's claim of compliance with an SAE standard is not evidence that SAE itself tested or approved the product. Ask for the test report.
What about SAE J1318? J1318 was the standard for gaseous-discharge (strobe) warning lamps. SAE canceled it in 2009, but older specifications can still cite it. If a specification references J1318, do not silently substitute a current standard; ask the specifier what they want.
Does Class 1 matter for scene lights or compartment lights? No. Those are work lights, covered separately in NFPA 1900, which uses illuminance and other criteria rather than warning-light classes. A warning lamp mounted inside the cab is still a warning device, though, so "interior" is not a shortcut for "not a warning light."
About this article: it was drafted with AI assistance, fact-checked against SAE, NFPA, GSA, California and NHTSA sources, and reviewed by K&K Emergency Systems. Standards change and errors are possible. Where we describe our own practice, it is our practice, not a requirement of any standard. Confirm any requirement with the standard, the manufacturer, or with us before you buy or install.