In this video, at the 6:25 mark, you can see a truck drive in front of the crawler, spraying water on the gravel ahead of the treads. Why did they do this?
According to https://www.popularmechanics.com/space/rockets/a15777930/launching-to-space-at-a-crawl/
it is to reduce dust created as the crawler crushes some of the "Alabama River Rock".
Photo showing the crushed rock behind the crawler. (Source - Organic Marble)
According to the documentary 'When We Were Apollo', the gravel was not part of the original design, but added as a sacrificial bearing surface to stop damage that was occurring to the internal bearings. (Which raises the question: is it raked after use, and periodically replaced?)