From the cyclingnews:
The crash happened just after the peloton descended down a bluff to cross the Broad River, 65km into the stage. Up to that point the terrain had been flat like the first two days, but the peloton was crossing the bridge at speeds reaching 80km/h when Collier's wheel became wedged in the concrete surface, sending him over the handlebars.
"I came out pretty lucky," said Collier. "Basically, it was the way I went down... as soon as we got onto that bridge, there was a seam in the concrete that swallowed my front wheel. It just came to a standstill when I crossed into it and I was vaulted over the bars.
That tells something.. :shock: