> taking the number of crashes per kilometer, and multiplying by the number of kilometers you'll drive for. A trip of 5000km is less safe than a 5km one.
When comparing a difference of 1000x, sure its probably safer.
Your premise is wrong though, it isn't common sense to take a generalized statistic like deaths per km and extrapolate that to be the correct estimate for any particular trip.
The statistic loses all context of differences in vehicles, road conditions, time of day, specific roads, etc. The stat is a great example of how a statistic seems meaningful to get a big picture but is completely useless to us as we can't make any decisions based on a number that is so generalized as to lose all context and meaning.