Do Window Breaker Tools Work on Laminated Side Windows?

No. In AAA's test of six vehicle escape tools, four broke tempered glass and none broke laminated glass, which "stayed intact even after being cracked". A tool is only as good as the window you aim it at, and you can check each window in about a minute: the printed block in a lower corner of each pane usually says LAMINATED or TEMPERED in plain capitals. AAA found that about 1 in 3 model year 2018 vehicles had laminated side windows, so do not assume your car is in the other two.

What the test actually showed, tool by tool

AAA tested three spring-loaded tools and three hammer-style tools on both kinds of side glass, and published the results in July 2019. Tool type mattered a lot on tempered glass and made no difference on laminated glass, because nothing worked.

Note AAA's wording: the laminated glass did crack. It did not open, and a starred pane still sitting in the frame looks like progress but is not an exit. And AAA's engineering director put the stakes in one line, that drivers who do not know their window type "could waste precious seconds trying to break glass that will not shatter".

Why no handheld tool opens a laminated pane

On tempered glass a breaker only has to push a hardened point through the thin compressed surface layer. Once the crack reaches the tension stored in the middle of the pane, the glass empties itself in a fraction of a second. How tempered glass stores that energy explains why a pen-sized tip succeeds where a fist fails.

A laminated pane has no stored energy to release. It is two thinner glass plies bonded to a plastic interlayer, the same construction as your windshield, and the interlayer stretches rather than tears. A punch fractures the ply it touches and stops. The film keeps every fragment in place. The interlayer that holds the plies together is the reason.

How to tell which glass is in each window

AAA's advice is to "check for a label located in the bottom corner of the side window", and that label is the glass maker's monogram, often called the bug. Read it on every pane, because a car can have laminated fronts and tempered rears.

1. Lower the window three or four inches. On door glass the bug often sits below the belt line with the window up.
2. Look for the word itself. Most side and rear panes print TEMPERED or LAMINATED, sometimes as part of a glass maker's trade name. That word is the answer. Reading the rest of the corner markings covers the DOT code, the M number and the logos around it.
3. Do not decide from the AS number. AS1, AS2 and AS3 are glazing classes that say where a pane may be used and how much light it must pass, under the federal glazing standard. They are not a construction label.
4. Confirm with the edge if the print is worn. With the window partly down, look straight at the exposed top edge in good light. Laminated glass shows a faint line through the thickness where the interlayer sits.
5. No word on the bug, or no bug at all. AAA's advice is to contact the vehicle manufacturer. A dealer parts counter can also look up the glass fitted to your VIN, as described in finding the part number for your glass.

Where to look first follows from the numbers. AAA's Oregon club, reporting the same test, put it at about 33 percent of 2018 models with laminated glass in the front side windows and only 4 percent with laminated glass in the back as well. The front doors are the likeliest laminated panes, and the rear doors the likeliest tempered ones.

What the federal ejection rule says, and what it does not

A common explanation for laminated door glass is that a federal rule requires it. It does not, and the rule does not let a roll-down window carry the load alone. FMVSS 226, Ejection Mitigation, at 49 CFR 571.226, states its purpose as reducing "the likelihood of complete and partial ejections of vehicle occupants through side windows during rollovers or side impact events". It applies to passenger cars, multipurpose vehicles, trucks and buses of 4,536 kg (10,000 lb) gross vehicle weight rating or less.

The test is specific. An 18 kg impactor carrying a headform is fired from inside the vehicle at target points in each side window opening, at 20 km/h and at 16 km/h, the slower strike timed 6 seconds after a rollover curtain fires. The outer surface of the headform may not travel more than 100 millimeters beyond the zero displacement plane, a vertical plane set at the headform's own outer surface before the strike. Before the test, the glass over each target must be "removed from the side daylight opening, fully retracted, or pre-broken", at the manufacturer's option. Then comes the sentence that settles the argument: "No vehicle shall use movable glazing as the sole means of meeting the displacement limit."

The 2011 final rule gives the reason. NHTSA reported that "31 percent of front seat ejections are through windows that were partially or fully rolled down", and that even glazing that starts up "may be destroyed and rendered ineffective" later in a rollover. Its expectation was that manufacturers would modify side curtain airbags, "possibly supplementing them with advanced glazing". The phase-in reached 100 percent of covered vehicles made on or after September 1, 2016. NHTSA estimated it would save 373 lives a year.

So curtain airbags carry FMVSS 226, and laminated door glass can add to them, along with a quieter cabin and slower smash and grab entry, covered in what acoustic glass does and what happens after a break-in. How retention fits the crash picture is in why laminated glass keeps occupants inside, and the other federal glass standards are gathered in the safety and standards section.

Spring-loaded or hammer: which to carry

Carry a spring-loaded punch. AAA's own summary is that "the spring-loaded tools were more effective in breaking tempered windows than the hammer-style", and its counts above make that three for three against one in three. A spring-loaded tool stores its energy internally and fires when you press it against the glass, so it needs firm contact rather than room to swing. AAA also notes that a hammer-style tool "could be much harder to swing underwater".

• Skip the extras. AAA advises avoiding tools with lights or chargers, "since these functions do not improve the performance of the tool itself".
• Test it once. AAA suggests testing it on "a softer surface such as a piece of soft wood".
• Get a belt cutter on the same tool. A jammed buckle or a loaded belt in an inverted car stops you before glass does.
• Mount it where you can reach it belted. Not the glovebox, not the trunk.

No tool in AAA's test opened laminated glass, so treat any product sold as a laminated glass breaker as untested, and plan around a tempered pane.

Which window to aim for

AAA's rule: "If the car has at least one tempered window, this will be the best point of exit in an emergency." Work it out in your driveway, in this order.

1. Try the switch first. If the window goes down, there is no glass to break. Breaking is the fallback.
2. Your nearest tempered side window. On a car with laminated fronts this is usually a rear door glass.
3. The back glass, if it is tempered and you can reach it. Read its bug too, since some are laminated. How rear glass is built and replaced covers the variations.
4. Not the quarter glass or the sunroof. One is too small for an adult, the other drops glass on you, as quarter and vent glass and sunroof failures describe.
5. Never the windshield. It is laminated on every road vehicle and bonded in to stay, which is the subject of how the glass behaves in a rollover.

Where on the pane to strike, how to clear the frame and the full submerged sequence are already set out in escaping a vehicle through the glass. If every side window in a sinking car is laminated, AAA's advice is to "move to the back of the vehicle or wherever an air pocket is located".

Where this answer stops applying

• The test is from 2019. A different tool or laminate has not been tested by this source.
• The 1 in 3 figure is for 2018 models. Only your own bug describes your car.
• Film changes tempered glass too. Aftermarket tint or security film can hold broken tempered fragments together as a sheet that has to be pushed out. Film on the inside of the glass covers what is usually on there.
• FMVSS 226 covers vehicles of 10,000 lb or less and excludes convertibles and walk-in vans.

What to do next

Tonight, read the corner of all four door windows and the back glass and write down which ones say TEMPERED. If you own a hammer-style breaker, replace it with a spring-loaded punch that has a belt cutter, test it once on soft wood, and mount it within reach of your belted seat. Then pick your exit window and tell the people who ride with you. For the front doors most likely to be the exception, read laminated side windows. If you have already had to break a pane, cleaning up tempered glass and covering a broken window get the car back in use. Side and rear glass replacement covers the new pane, and what side glass costs shows why a laminated door runs higher.

Frequently asked questions

Can a spring-loaded window punch break laminated glass?

Not in AAA's test. All three spring-loaded punches broke tempered glass, and none of the six tools broke laminated glass, which cracked and stayed in the frame. The punch has nothing to release in a laminated pane, because the plastic interlayer holds both glass plies together. Use it on a window you have confirmed is tempered.

How do I know if my car windows are laminated or tempered?

Lower each window a few inches and read the printed block in its bottom corner. Most panes spell out LAMINATED or TEMPERED. Check every door and the back glass separately, because fronts and rears often differ. If there is no word or no label, AAA suggests asking the vehicle manufacturer, and a dealer can look up the glass by VIN.

Are hammer-style escape tools any good?

They are the weaker choice. In AAA's test only one of three hammer-style tools broke tempered glass, against all three spring-loaded tools. A hammer also needs room to swing, which you may not have when belted in, and AAA notes it could be much harder to swing underwater. A spring-loaded punch only needs firm pressure.

Does federal law require laminated side windows?

No. FMVSS 226 requires side window openings to keep an 18 kg test impactor within 100 millimeters, but it bars roll-down glass from being the only countermeasure. NHTSA expected manufacturers to use curtain airbags, possibly supplemented with advanced glazing. Many cars still have tempered door glass, so read the label on yours.

Which window should I break to escape my car?

Whichever side window you have confirmed is tempered and can reach, which on many cars with laminated fronts means a rear door. A tempered back glass is the next choice if the cargo area is reachable. Never plan on the windshield, the sunroof or a small quarter window. Try the window switch before breaking anything.