When I was a kid I worked in a double glazing factory. Some of the old timers demonstrated just how hard it is to break a piece of toughened glass to me by whacking one with a bit of wood right in the middle of the pane, really really hard. Nothing happened. Then the dude tapped it really quite gently with a glass breaker in the corner (where it can't flex as much he said) and the whole thing exploded into those little cubes you see on the ground in dodgy car parks.

Car windows are probably harder to break than you think...lol. Also - consider the situation where the car is in, or partially in water, and pressure differentials.

(There was actually another HN thread about this recently - https://news.ycombinator.com/item?id=39691780).

I keep a Resqme in the car glovebox - my other half used to do a lot of interstate driving, and I was always worried she'd be trapped in the car. The Resqme has both a seat-belt cutter, and also a centre-punch for easily breaking the side windows.

This is a genuine question: how useful is the resqme in a glove box? Do you think the driver could reach it in the event of an accident, or do you keep it so the passenger can use it to free the other occupants?

I'd clip it to the seat belt pulley. But round here you'd have difficulty reaching speeds to have a crash, what with all the minis doing 20 under the limit

Side windows in most new cars are also laminated. The quarter windows are the one you should try break.

There is a mythbusters episode about exactly this that is definitely worth the watch.

windows are normaly tempered glass. You can't kick them out.

They're also unbelievably strong when they're completely rolled up and incredibly weak when they're not.

Although a tiny piece of ceramic at just the right speed will shatter any window.

And I recommend a spring-loaded window breaker, as opposed to having to, like, physically hit the thing against the window.