What VSI 26 actually is
VSI 26 is short for Vehicle Standards Information 26, "Roadworthiness requirements." It isn't a windscreen shop's house rule or an insurer's internal guideline. It's issued by Victoria's own Department of Transport and Planning, as the written directions the Secretary gives under Regulation 251 of the Road Safety (Vehicles) Regulations 2021. That's the same government body that sets what a licensed vehicle tester has to check, on every roadworthy inspection, on every car in the state.
The current edition is dated March 2023 and says outright that it supersedes every earlier copy of VSI 26. An older, February 2017 edition of the same document exists too, issued under the predecessor regulation, and it states the identical figures. Two editions, six years apart, same numbers. That's not a coincidence. It's a genuinely stable line, not one that shifts with whoever's doing the inspecting.
A roadworthy certificate is issued by a licensed vehicle tester, in person, looking at your actual car. This tool reads the same document that tester is working from and applies it to what you describe. It doesn't replace the inspection. Nothing that follows here does either.
Why the wiped area is what decides it
Here's the part most drivers get wrong, understandably, because it's not obvious from just looking at a chip. VSI 26's measured limits don't apply to the whole windscreen. They apply to the area the wiper blades actually sweep. Section G says a windscreen should only be rejected if it "is discoloured, badly scratched, fractured or chipped within the area wiped by the windscreen wiper(s) to the extent that the driver's vision is so impaired that the vehicle cannot be driven safely", and separately, for the measured bulls-eye, star and crack limits, within that same wiped area.
A star fracture the size of a fifty-cent piece down near the passenger-side corner, well clear of where either wiper blade ever travels, isn't weighed against the same rejection criteria as identical damage sitting dead centre in front of the driver. Same glass, same impact, two different positions on the pane, two different answers under this document. It's worth checking where your own wipers actually reach before you measure anything else, because that single fact changes which part of the standard applies to your damage at all.
I'd guess this is also why so many roadworthy fails on windscreens surprise people. A chip that's been sitting there for months, ignored because it's small, turns out to be right in the driver's critical line of sight the whole time.
Bulls eye, star fracture or crack: three shapes, two limits
Stone-chip damage doesn't come in one shape, and VSI 26 doesn't measure it as though it does. A bulls eye is a roughly circular impact mark, often with a dark centre where the layers have separated. A star fracture is the same kind of impact, but with cracks radiating outward from the point of contact, like a tiny spiderweb. Both are measured the same way in the document, by diameter, and both carry the same 16mm figure. A crack, a longer line running across the glass rather than radiating from one point, is measured by length instead, and carries the 150mm figure.
Quoted directly, the standard treats these as one rejection criterion, in the wiped area, for a laminated windscreen that "has one or more bulls eyes or star fractures over 16mm in diameter or one or more cracks over 150mm in length in a single layer of glass." And it states the flip side just as plainly: damage "up to 16mm in diameter and cracks up to 150mm in length in a single layer of glass within the area wiped by the windscreen wiper(s), are allowable provided that they do not impair the driver's vision to the extent that the vehicle cannot be driven safely."
That last clause matters as much as the number. Being under 16mm or 150mm doesn't mean automatic clearance, full stop. It means the specific numeric rejection doesn't apply, and the general vision test still does. Worth sitting with for a second. A tester looking at a 15mm bulls eye smack in the driver's eyeline, on a low winter sun, could reasonably decide it still impairs vision enough to fail the general test, even though it clears the measured line on its own.
Why penetrating more than one layer changes the answer
A windscreen isn't one sheet of glass. It's laminated: two layers of glass bonded to a plastic interlayer in between, which is exactly what stops the windscreen shattering into loose shards in a crash and instead holds it together as one flexed sheet. Most stone-chip damage only reaches the outer layer. That's the ordinary case VSI 26's 16mm and 150mm figures are written for.
A crack that goes deeper, through more than one of those layers, is treated differently by the document, and there's no size exemption written into that part of it. VSI 26 states a laminated windscreen "should only be rejected if... in the case of a laminated windscreen, it has any crack that penetrates more than one layer of glass." No 150mm figure attached. "Any crack" is the actual wording. That damage has already gone past what a resin injection is meant to fix, because the whole reason a laminated screen still holds its shape is that plastic interlayer, and once a crack has reached it, the size of the mark on the surface stops being the thing that matters.
What a proper repair looks like, and why it still passes
This is the bit that catches out plenty of people who assume "repaired" and "invisible" are the same thing. They're not, and VSI 26 says so directly. A competent resin repair leaves a mark. The document's own words: "In a repaired windscreen a faint outline of the repaired damage or in some cases a slightly dull spot may be visible where the repair has been performed. A repaired crack may also be detectable by a fine hairline surface mark. These are acceptable and should not be rejected during a roadworthy test providing the rest of the windscreen complies."
So a tester seeing a faint circular shadow where a bulls eye used to be shouldn't be treating that as a fail. Neither should a fine surface line where a crack was injected and cured. That's what a properly done repair is supposed to look like once it's finished, not a flawless, invisible patch. If a resin repair genuinely vanished without any trace at all, that would honestly be the more surprising outcome. The resin's refractive index is close to glass, not identical to it.
What this passage doesn't excuse is a bad repair, one where the resin didn't fully fill the break, or where a star fracture's legs weren't properly sealed and kept spreading afterward. "These are acceptable" is talking about the faint mark a good repair leaves, not about damage that was patched over rather than actually fixed.
Why a small chip turns into a long crack
A stone chip you could genuinely ignore for months has a habit of not staying that way. Glass moves with temperature. Park a dark-coloured car in full Melbourne summer sun, then blast the air conditioning on high the second you get in, and that fast temperature swing across a small weak point is exactly the kind of stress that turns a 4mm bulls eye into a crack running most of the way across the glass overnight. A pothole, a door slammed a bit too hard, even the car's own chassis flexing slightly as it ages, can do the same thing to a chip that was sitting well inside the safe range.
That's the actual argument for getting a small chip looked at sooner rather than later, and it's not really about the roadworthy test at all. It's that a $150 resin repair, done while the damage is still small, is what keeps a car out of the far more expensive replacement category later. Once a chip has grown into a genuine crack over the line, or run into more than one layer, the repair option is usually gone, and it's gone for a reason that had nothing to do with the original stone strike.
When it's a repair, and when it has to be a replacement
Reading VSI 26 straight through, three things push a job from repair to replacement territory: the crack has gone through more than one layer of the laminate, the measured size is over 16mm for a bulls eye or star, or over 150mm for a crack, within the wiped area, or the damage sits somewhere the driver's vision is genuinely affected regardless of the measurement. Clear of all three, a resin repair is realistically on the table, and it's the cheaper, faster job by a wide margin.
But get a couple of quotes before you commit either way, and ask whoever you call to actually measure the damage rather than eyeball it through a phone photo. A technician who tells you it needs replacing without measuring anything is worth a second opinion. One who wants to inject resin into a crack that's already run past 150mm, in the wiped area, is trying to sell you a fix the standard itself doesn't treat as sufficient.
The honest limit here
This tool measures your damage against VSI 26's own numbers, the same ones a licensed vehicle tester is working from. What it can't do is stand in the driver's seat and check whether a chip that's technically under 16mm still sits right where your eyes track the road, in low sun or heavy rain, in a way that genuinely makes the car unsafe to drive. That's a judgement call, and VSI 26 deliberately leaves it as one. It says damage under the measured limits "are allowable provided that they do not impair the driver's vision to the extent that the vehicle cannot be driven safely", not "are automatically fine."
Only a licensed vehicle tester, looking at the actual glass in the actual car, can make that call. If your result above sits close to either line, 16mm, 150mm, or right at the edge of the wiped area, book an actual roadworthy inspection rather than treating this page as the final word. It's a starting point for knowing what you're walking into, not a certificate.