# Semi truck markings and license plate questions - history thereof **URL:** \ **Category:** Factual Questions\ **Created:** [October 16, 2022, 6:49am UTC](https://boards.straightdope.com/t/semi-truck-markings-and-license-plate-questions-history-thereof/973324 "2022-10-16T06:49:31Z")\ **Posts on this page:** 6\ **Page:** 1
**Author:** ![Just\_Asking\_Questions](https://avatars.discourse-cdn.com/v4/letter/j/ba9def/32.png) [@Just\_Asking\_Questions](https://boards.straightdope.com/u/Just_Asking_Questions)\ **Post date:** [October 16, 2022, 6:49am UTC](https://boards.straightdope.com/t/semi-truck-markings-and-license-plate-questions-history-thereof/973324/1 "2022-10-16T06:49:31Z")
It’s surprisingly hard to find the answer to my questions. I can get tons of sites telling me how to install the marking, which markings are correct, what they mean - but the history is obscured. When were trucks first required to use red and white reflective tape? My memory says it was about 1999-ish? [![](https://m.media-amazon.com/images/S/aplus-media-library-service-media/d300c99a-4a09-4092-98a4-aea99b9c7e90. __CR0,0,970,600_PT0_SX970_V1___.jpg) ](https://m.media-amazon.com/images/S/aplus-media-library-service-media/d300c99a-4a09-4092-98a4-aea99b9c7e90. __CR0,0,970,600_PT0_SX970_V1___.jpg) When were trucks first required to use the four digit UN code for hazardous cargo? I remember when tanks trailers were labeled “HAZARDOUS CHEMICALS” and whatnot, and fire departments were left to fend for themselves to figure out what actually was in the trailer. Now we have the UN code, which makes it easy. But. when did we switch over? [![](https://danielstraining.com/wp-content/uploads/2014/05/100_3810.jpg) ](https://danielstraining.com/wp-content/uploads/2014/05/100_3810.jpg) When did trucks switch from many license plates to one single “apportioned” license plate? The 1990s? Then: [![](http://forums.aths.org/InstantForum2010/Uploads/Images/4dc01686-688e-44ff-8fa2-408c.jpg) ](http://forums.aths.org/InstantForum2010/Uploads/Images/4dc01686-688e-44ff-8fa2-408c.jpg) Now: [![](https://cagtruckcapital.com/wp-content/uploads/2018/05/peterbilt-truck-financing-testimonial-randy-KY-600x403.jpg) ](https://cagtruckcapital.com/wp-content/uploads/2018/05/peterbilt-truck-financing-testimonial-randy-KY-600x403.jpg) ---
**Author:** ![bob\_2](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/bob_2/32/3341_2.png) [@bob\_2](https://boards.straightdope.com/u/bob_2)\ **Post date:** [October 16, 2022, 1:38pm UTC](https://boards.straightdope.com/t/semi-truck-markings-and-license-plate-questions-history-thereof/973324/2 "2022-10-16T13:38:16Z")
Googling round, it gets confusing. The relevant regulation seems to be **49 CFR 390.21 - Marking of self-propelled CMVs and intermodal equipment.** October 1, 2011. > **[GovInfo](https://www.govinfo.gov/app/details/CFR-2011-title49-vol5/CFR-2011-title49-vol5-sec390-21)** > > Official Publications from the U.S. Government Publishing Office. However, I also read this: At [82 FR 5316](https://www.law.cornell.edu/rio/citation/82_FR_5316), Jan. 17, 2017, § 390.21 was suspended, effective Jan. 14, 2017. At [84 FR 40294](https://www.law.cornell.edu/rio/citation/84_FR_40294), Aug. 14, 2019, the suspension was lifted and amendments were made to § 390.21. In that same document, § 390.21 was again suspended indefinitely. > **[GovInfo](https://www.govinfo.gov/app/details/CFR-2011-title49-vol5/CFR-2011-title49-vol5-sec390-21)** > > Official Publications from the U.S. Government Publishing Office. ---
**Author:** ![Just\_Asking\_Questions](https://avatars.discourse-cdn.com/v4/letter/j/ba9def/32.png) [@Just\_Asking\_Questions](https://boards.straightdope.com/u/Just_Asking_Questions)\ **Post date:** [October 17, 2022, 8:03pm UTC](https://boards.straightdope.com/t/semi-truck-markings-and-license-plate-questions-history-thereof/973324/3 "2022-10-17T20:03:46Z")
One more bump for visibility, in case anyone knows. ---
**Author:** ![silenus](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/silenus/32/166_2.png) [@silenus](https://boards.straightdope.com/u/silenus)\ **Post date:** [October 17, 2022, 8:27pm UTC](https://boards.straightdope.com/t/semi-truck-markings-and-license-plate-questions-history-thereof/973324/4 "2022-10-17T20:27:02Z")
> [@Just\_Asking\_Questions](#): > > Now we have the UN code, which makes it easy. But. when did we switch over? 2011? [https://www.federalregister.gov/documents/2011/01/19/2010-33324/hazardous-materials-harmonization-with-the-united-nations-recommendations-international-maritime](https://www.federalregister.gov/documents/2011/01/19/2010-33324/hazardous-materials-harmonization-with-the-united-nations-recommendations-international-maritime) ---
**Author:** ![Chronos](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/chronos/32/134_2.png) [@Chronos](https://boards.straightdope.com/u/Chronos)\ **Post date:** [October 17, 2022, 8:36pm UTC](https://boards.straightdope.com/t/semi-truck-markings-and-license-plate-questions-history-thereof/973324/5 "2022-10-17T20:36:02Z")
I’m guessing that part of the uncertainty might be due to some regulations being first implemented by various states, before being set nationally by the federal government. So for some period of time, you’d have some trucks (those that at least partially operated in those states) with the new markings, and some without. ---
**Author:** ![Skywatcher](https://sea3.discourse-cdn.com/straightdope/user_avatar/boards.straightdope.com/skywatcher/32/254_2.png) [@Skywatcher](https://boards.straightdope.com/u/Skywatcher)\ **Post date:** [October 17, 2022, 8:57pm UTC](https://boards.straightdope.com/t/semi-truck-markings-and-license-plate-questions-history-thereof/973324/6 "2022-10-17T20:57:16Z")
> [@Just\_Asking\_Questions](#): > > When did trucks switch from many license plates to one single “apportioned” license plate? The 1990s? For the most part, yeah. [The government-sponsored organization responsible for this started with three states – Kentucky, Missouri, and Tennessee – in '73 and went national in the US & Canada in '91.](https://www.irponline.org/page/History)