Sentence:  Which means that for every car there was 10 years ago, there are now 40. Which means - and this is my own, not totally scientific, calculation - that the <WSD>space</WSD> between cars on the roads in 1991 was roughly 39 car lengths, because today there is no <WSD>space</WSD> at all. 
Meaning of the word marked with <WSD> tags:  Distance between things. (from 14thc.)