It was the same, when there was the (supporting) sportive, with the 'Tour de Yorkshire'
I rode up, from the (Wakefield) start on Sunday, to watch the climb of East Chevin, heading up through Leeds, past Yeadon Airport (Leeds-Bradford), & got caught up in it, as they turned down Harrogate Road, towards the cross-roads with Leeds Road (A660), towards Poole-in-Wharfedale
It was scary, bikes overtaking on both sides, over-taking cars downhill on double solid whites!!
I'll hazard a guess that the traffic-lights on the cross-roads at the Dyneley Arms weren't treated correctly by quite a few
I was extremely happy, & relieved, to turn left towards Otley
The Chimps in the old PG Tips adverts were far better riders than some I saw
What I saw, even in that one case, could make a case for limiting numbers/sanctions on Sportives, if seen by a Senior Police Officer, or local MP