Well, first of all, there are certain provisions to be made, and I am not by any means complete:
1. Although Pascal is inheritantly safe, it allows for unsafe constructs because it allows for e.g. C style strings, a.k.a. PChars. Code that does not rely on Pascal string types is just as unsafe as C is.
2. It takes, given the modern Pascal syntax, programmer discipline, not compiler discipline, to write safe code, but that can also be done in any given language. A disciplined C programmer can also write safe C code.
3. Although I welcome the mention of Pascal as being safe, this is in my opinion simply not true.
Then again, I am perfectly capable of writing unsafe code - using attributes, unckecked_access - in ADA, the safest of all safe languages)
So I am still a bit bemused why Pascal ranks so high.. It isn't as safe as suggested.
What is true, though, that if a programmer sticks to just native Pascal types, the language is a lot safer than others.
(Also note that most ADA compilers will warn you if you do as I suggested!)
What makes code more safe, in any language, is peer review.