My local bus in Chengdu says this on the emergency exit window:

紧急情况下用安全锤击碎应急出口玻璃撒离！

Two questions.

1. What is the function of 应急 here? Is it modifying 出口, as in "emergency exit"? Or is explaining the purpose of 击碎, as in "strike in an emergency"?

2. Except for exclamation mark, there's no punctuation in this sentence. Should there be? To my eyes 玻璃撒离 is a separate clause from what comes before.

The way I read it:

紧急情况下 in case of emergency
用安全锤 use the safety hammer
击碎应急出口玻璃 to break the emergency exit glass
撒离 to evacuate

Does 撒离 mean evacuate? I checked a few dictionaries but didn't find anything. 撒 means scatter, which I assumed referred to the broken glass.

玻璃撒离：The glass scatters 玻璃撒 and you leave 离.

But I'm guessing. Anyone else?

1. Yes, MBDG at any rate puts it together, so 应急出口 'should urgent exit' / emergency exit.

2. I'm not at all sure on 撒, but I think it's more likely it's modifying the 离. Let go (as opposed to scatter) and leave. Same ball park...

It’s not 撒离 but 撤离. Here, 撤 [chè] means “withdraw, evacuate.”

Yes that's it, thanks! I must have made a mistake copying the text into my phone. And there it is, yet another reason to keep learning Chinese characters...

This solves my punctuation question, too.

紧急情况下用安全锤击碎应急出口玻璃撤离！

In case of emergency use the safety hammer to break the emergency exit window and evacuate.

Reminds me of the instructions in the Shanghai subway (in Chinese - from memory so it's a bit off):
1) Uncover exit control cover
2) Twist stop lever
3) Make sure train is stopped first

In my mind #3 really should be #1!