There were a group of people

"a" group = one group = 1 group

Regardless of how many people are members of that group, it is still referred to as a single unit -- so you must use is or was.

On the other hand, if there are 2 or more different groups trying to block the road, you would use are or were.  If one is a group of Martians and the other is a group of Elves, and they were both trying to block the road, then you would say, "There are 2 groups..." or "There were 2 groups..."

- Arvin G.

Think about it!  This is really more logical than you think.

There is a group.

There is only one thing - a group - singular.

People are trying to block the road - more than one person - plural.

So, people who (i.e., they) are trying to block the road.

The single group is composed of more than one person.

[There is a group of (composed of)] [ people who are trying to block the road].

CJ

a couple of, a number of, and several others are the exceptions.  They are "number transparent".  That is, the agreement is with their complements, not with their heads.  There are a [couple / number] of people ...

CJ

CalifJim wrote:

Think about it!  This is really more logical than you think. There is a group. There is only one thing - a group - singular.

Hi Jim

I agree with you but with English more than one kind of logic apply, in actual usage anyway. It is true that 'there is only one thing  -  a group'. In BrE in particular, a plural verb is often used when 'there is only one thing': England are winning. Only one country is mentioned but the England team consists of many players. By the same logic, a group consists of several people and consequently many people wouldn't hesitate to say: there were a group of people in the street. (I am one of them.)

Liberal grammarians don't find that objectionable. According to these usage experts, the choice of the verb is quite free in English:

There is/are a book, a pen and a pencil on the table.

But, as I said, there is nothing wrong with your logic. I just wanted to mention another way to look at the matter, a way favored by many.

Cheers
CB

CalifJim wrote:

The cases with there is / there are are almost a separate class by themselves.  In informal language (in the U.S.)  you can use the contraction there's (but not there is) with just about anything.

Oh, yes, exactly. I know that, but I didn't mention it because it would have complicated matters (I was actually only interested in the choice between singular and plural verbs). Anyway, thanks for pointing that out, it's always useful to get some more information, I'm more likely to learn something new.
It seems that "there's" is pretty common (in the US, at least). I also remember hearing that in a video we discussed here, in another section of this forum: "How many sides does a triangle have?" - "Uh, uh, there's no sides."

Thanks again to you all for your opinions.