Explain the significance of Clarisse's speech about "blurs". Why are billoards 200 feet long?

Clarisse's speech is significant because we come to see how fast life moves in their society. No one takes the time to look around and see what's out there, thus, this also explains the 200 ft. long billboards..... if they were any smaller, they'd never be seen.

Clarrise, and her speech is the most significant reason why Montag questioned not only himself and his happiness but also question the way of society. Her speech implies that people don't just stop and look at the world anymore, everything is just a big blur. Symbolizing the world and technology as progressing to fast.