I am trying to run down an online rumor based on no factual evidence that car manufacturers (one person mentioned Porsche specifically) have to do crash tests of all seat belt designs, even if the only difference is the color.
Back in the early 80s I worked for Ford doing crash test analysis (we did not like to say “crash test” and called them “barrier tests”) and in my experience this requirement would not make sense. At that time, the car companies did tests to make sure that the cars would pass any random tests that the government did. I don’t recall that we had to submit test results to the government to get any kind of certification (I think we did have to do that for emissions standards). Even if they now have to certify their tests with the government, there are so many different designs of so many details that it’s not feasible to test everything like that, and I’m sure the government is at least a little bit rational about it.
Is there an authoritative source that describes what testing is required?
I have not worked on automotive crash testing (other than once working on some airbag simulations in Abaqus as a contract job which required interpreting crash data) but it would not make sense to test every possible permutation of seat belt color. I know that many vehicles are only tested in one of multiple chassis and body variations depending on similarity, and you could easily demonstrate that seatbelts with different color meet some minimum required tensile and elasticity specification without having to crash an entire vehicle per option. (It may be the case that there are slight variations in the tensile strength because effects of the pigmentation or processing but there is so much margin put into the seatbelt material and the way it is woven that it shouldn’t matter.)
As far as crash testing requirements, for the United States there are two different bodies: the National Highway Transportation Safety Administration (NHTSA), which is a branch of the United States Department of Transportation which imposes mandatory minimum requirements for testing and safety and provides the ‘vaunted’ “5-Star Safety Rating” (which isn’t actually all that selective); and the non-profit Insurance Institute for Highway Safety and Highway Loss Data Institute (IIHS-HLDI) which actually has a more comprehensive set of safety performance tests including crash avoidance, mitigation (driver assistance), and automation that are used by insurance companies to assess comprehensive vehicle safety. The latter provides a menu of tests that automakers can opt to perform and report on or not but most do because it looks bad not to submit vehicles. The tests, particularly the IIHS tests, are frequently upgraded so there is no standard baseline across years of production, and the same vehicle may be required to undergo new tests if the vehicle design or the test standards have significantly changed.
Europe has a different set of standards (with which I am not familiar beyond some of the tutorials in RADIOSS referring to them), which creates homologation issues (mostly in selling American vehicles in Europe, but because the standards are different the NHTSA and most IIHS tests have to be run on European vehicles imported into the US, and I’m sure the same is true with Japan, South Korea, et cetera). Sweden famously had the “Moose Test” (later codified as ISO 3888-2) where the vehicle had to perform an extreme swerve at a near-cruising speed without overturning or losing control. (Volvo and Saab would also literally run their vehicles into a simulated moose target to demonstrate the safety of the vehicle in a collision, which for anyone who has hit a moose or even a whitetail deer should be pretty impressive.)
Anyway, I’m morally certain the story you’ve been fed about crash testing trivial variations in seat belt designs is mostly if not complete bunk.
I thought to have a look at the standards that apply in the UK. Regulation 47 of the Road Vehicles Construction and Use Regulations 1986 is the relevant law, but while it goes into a lot of detail about the fitting of seat belts the actual specification of the belt material is defined in BS 3254; 1960 and BS AU 160a or 160b. (BS = British Standard). I tried to look them up but it cost £150 to download, so that was as far as I got.
No, color is not taken into account in crash testing. They build up what they call Body In White vehicles for crash test purposes at each of the pre-production builds and the bodies are actually white. The interiors themselves may not actually be complete interiors, depending upon the requirements and nature of the testing being performed.
For instance, if they are testing for an issue with the front dash they may not even have anything beyond the the first row, including no rear seats. Running physical testing is costly and time consuming, so the OEM’s plan out the testing to minimize the cost.
Also as a side commment, it is illegal to use parts from a crash test on a production level vehicle meant for using on public roads. I’ve known people who were fired for taking rims and tires from crash testing and using them on their own cars.
I’m sure the different colors of seat belt webbing are themselves tested for tensile strength, etc… under the assumption that possibly the dyeing process might have changed their properties and to ensure that they meet whatever minimum standard they’re supposed to meet, but like you say, at the point when they’re being integrated into a seat belt system, they’re assumed to meet the standard, and are just integrated into the system.
This is perfectly plausible. You can’t make color the only difference. The color is different because some ingredients are different. I think it’s even possible that some colors (darker or more red or yellow) provide some protection against long term sun damage.
Wasn’t it once the case that blue car paint used to be more prone to failing with time?
IIRC, if you buy cable ties specifically for use outdoors, they’ll be black. The black helps prevent damage from sunlight.
As to whether they are actually required to test all the colors, I don’t know.
FWIW, back when I was in cell phone development, we absolutely did mechanical and RF testing on different color housings. They would degrade differently in accelerated life testing, and could potentially have different RF characteristics.
I’d easily believe that mechanical properties need to be verified at some point.
A seat belt supplier would define the webbing as a given material with demonstrated chemistry, manufacturing, and adherence to a variety of environmental and mechanical tests to demonstrate that the webbing, when used, always performs in this manner. They would generally demonstrate that the available colours meet these requirements, though some tests may be omitted in some cases for a new color (adding less of a dye that’s already been demonstrated can be qualified by similarity). In fact, for tests like flammability there are acceptable means of compliance that rely on this; burn testing of one colour of a given chemistry webbing substantiates another. The same is true for paint chemistry and things like laminate or synthetic leather (“ultra leather”). It is not true of natural fibers like wool or leather.
The seat belt/harness installed on a seat has additional testing, as it now has it’s own engineering definition (part number) consisting of specific buckles, attachment fittings, stitch lines, etc. As any colour webbing of a specific definition is equivalent, these assemblies can be substituted with relatively little paperwork as well.
There are published minimum performance standards for seat belts, such as TSO-C22 which are public information, though they cite non-public documents like SAE standards.
In general most seat belts are supplied in two shades, light and dark to match the interiors. Some high end models with many color options, like the Corvette can have many options.
Still the color plays no part in crash test. It is the suppliers responsibility to perform testing on indivudual variations and ensure that they meet the OEMs specifications. There is a chain of testing requirements that must be meet before an OEM performs a crash test. Crash testing is serious business and they do not have the resources to test for things like color differences.
I work for an automotive OEM and we have a crash test facility next to my office. And I attend the builds where they make the vehicles for all test teams, not just crash test.
Yeah, I used to work for a major helicopter manufacturer, and one morning I came in to find our logistics guys freaking out, because they found out that some of our larger clients had been using John Deere tractor bearings in their helicopters, which weren’t FAA-approved.
Thing was, the bearing supplier sold the exact same bearing to us under a different part name, and we went through the trouble for FAA certification, then sold it for 3x the price. So really not any safety issue or anything, just FAA certification paperwork and 3x the price.
Arguably the safety issue is the evidence. You know it’s safe because you have the paper trail, you know? Otherwise it’s just a hunk of metal that may or may not be what you think it is, and there might not be a way to figure it out without destructive testing.
The risk involved is the difference maker. A bearing that fails on a tractor might leave you parked in the middle of a cornfield, which is inconvenient but not catastrophic (bears and homicidal cows and whatnot notwithstanding). A failure on a plane or helicopter could have it fall from the sky, which would likely hurt at least as much as dealing with the cows.
I agree it’s a pain in the ass, but I also wholeheartedly feel it’s necessary.
For non-critical items, it is possible to certify commercially available parts, in some cases. I’ve done it. But it can be nearly as much of a pain in the ass and usually it’s not my money being spent so it’s not worth it!
Having worked on a number of campaigns to uncover counterfeit components (fasteners, batteries, aluminum alloys used in forgings) I can attest to this being the case. The complaints that are often herd about how defense or aviation contractors spend multiples of the cost to purchase a bolt that is functionally the same as can be purchased at Fastenal or down at Home Depot from a bin ignore that in many of these use cases the strength and durability of the fastener is critical and a failure can be catastrophic. It is also the case that a component might appear to be something that is the same as a commercial part but is actually certified to have very tight dimensional tolerances and specific mechanical/electrical/corrosion properties that require tight production controls or ‘cherry-picking’ acceptable units from a larger production lot.
Maybe 25 years ago I wanted to pick up a child’s car seat for the infrequent times I might need one. I found a seller at the local flea marker who had several nice looking seats at a considerable discount over the new cost. As I looked over a model I liked I could see that the seat belts had been cut at some point and resewn using ordinary thread in a simple stitch. Not the back and forth, double overlap criss-cross like an original. I pointed this out to the seller and mentioned it was illegal to modify a child’s seat in such a fashion. It did not go well. Let’s just say I might have met one of the first “Karens”.
It’s advised to cut seat belts on expired car seats, or on ones that have been involved in a crash, even a low impact one (follow manufacturer’s recommendations on that).
I can imagine someone collecting these from garbage days and trying to make a buck after “repairing” them. How reprehensible.
As with most safety related items, a given set of performance characteristics have been demonstrated, and anything outside that set is simply unknown. I’ve known people to complain about expiry dates, and it’s true there’s no “time bomb” where the seat was safe on day n and not on n+1 but there simply isn’t any data about n+1 and subsequent. There’s proof until n, no proof after. Similar with minor accidents; while they are designed to withstand certain loading to protect the occupant, they are shown to do this once. There’s no data on the car seat behavior after loading, deformation, etc to tell you it’s as safe as it was. It’s perhaps possible to do non destructive testing and evaluate that data, but getting someone out to do that kind of work would far exceed the cost of a new seat! Car insurance often covers replacement costs anyways (like for like; my husband got a replacement after he was rear ended even though the car seat wasn’t occupied at the time).