collective-nouns
For rental agencies and companies, the cars owned would be a fleet. Several cars escorting a VIP would be a motorcade.
However, what if I want to say:
I dislike being the lone driver in an empty stretch of highway, so I may end up speeding to get from the [group of cars] behind me to the [group of cars] in front.
Is there a good collective noun that would apply to this situation? Or would it be a matter of choosing a general term, like group, cluster, block etc.
In English, or at least in the US, we normally group students by the year of graduation rather than the year of entrance. We would say you're part of the "Class of 2010." If we need to group by year of entrance, we would probably say you're part of the "Freshman Class of 2006."
It is called a bed or a nest.
Source: http://www.thealmightyguru.com/Pointless/AnimalGroups.html
Bed and nest are mentioned as a collective noun for scorpions in various sources also.
I did a search on Google Ngram for "nest of scorpions", "bed of scorpions","colony of scorpions" and "group of scorpions". Ngram couldn't find "colony of scorpions" and "group of scorpions". Below is a screenshot:
Google Ngram result for "a nest of scorpions":
Though, nest can be used in the sense below also:
(Zoology) a number of animals of the same species and their young occupying a common habitat: an ants' nest.
Best Answer
Since there appears to be no exact technical term for a bunch of independent cars traveling together on a thoroughfare, you will have to go with broader terminology. I would prefer to say group of cars (which is what you started with) or even just cars as Oldcat proposed. Since there isn't a specialized term for it, many variations of this will be understood just as well.