[CalRobert]

I can assure you most drivers don't concern themselves with providing huge safety margins.

Also, when you have a decent number of cyclists and congested roads they often do travel in packs. See here for an example

https://www.youtube.com/watch?v=h-4ynw8672A

or here

https://www.youtube.com/watch?v=xhuxmiNsHmA

The city in these videos has many cyclists (and one of the most successful bike-share schemes in the world), but rather scandalously provides very little bike infrastructure and even less enforcement (bike lanes are generally used for parking).

Finally, you might wish to note that one generally refers to "riding" a bike in English, rather than "driving". The same goes for motorcycles in most contexts. This is different from some other languages, such as German, where the same word is used for operating all of those conveyances.