grammatical number - Is this compound noun compose of a group of many things plural or singular?

In the following sentence, I'm not sure whether the noun should be considered plural or singular?

A grid pattern of streets (Main, Elm, First) are shown.

Or:

A grid pattern of streets (Main, Elm, First) is shown.

The grid is clearly singular, but streets is plural. I'm thinking it should be singular because the grid contains the streets, but am not sure. Which one is correct?

Answer

In this case, the compound grid pattern is clearly singular. There are some words in English which will take their number from the number of the noun within their complementary prepositional phrase, but pattern is not one of those nouns. Therefore, I would always use:

A grid pattern of streets is shown.