In Japanese, these aren’t noun suffixes but number suffixes, known as counters or classifiers. You don’t say, “*ninjin ga san” [three carrots], but rather, “ninjin ga sanbon” [three-cylinder-shaped carrots].
Mass nouns behave in a similar way in English: you don’t say “*three breads”, but rather, “three loaves of bread”. Also, “head of cattle”, “slices of toast”, “sheets of paper”, “items of cutlery”, etc.
In Navajo, the classifiers are verb stems.
Deaths per cyclist per kilometre of road is a crazy unit of measurement. I mean, sometimes you have to report the statistic you’ve got rather than the statistic you’d like, but I don’t see what possible practical significance this has.
The statistic we’d like to know is deaths per kilometre cycled. The average person in the UK cycles about 60 km a year (source: Department for Transport) and the population of London is about 8.5 million (source: Wikipedia), so the 19 deaths in 2006 correspond to about 3.5 deaths per 100 million kilometres cycled.
This is slightly higher than the UK average of 3.1 deaths per 100 million kilometres cycled, and on the high side for Western Europe (compare Netherlands: 1.0; Germany: 1.8; France: 3.1; Italy: 3.4).