I'm not thinking of doing one or anything silly like that, it's more a question of organisation.
The bike leg of a triathlon is basically a TT, Olympic ones being 40K makes it give or take a 25 in the middle or the event. What rules are there to where you can do them, what times you can run them, size of field etc. I'm not after umpteen rules and regs it's more a case of curiosity.
With a TT it is controlled as to what roads(courses) you can use at certain times, and when you have to be off the road by - hence a lot of the early starts. Traffic counts have to be done at times when the races would be run to confirm the volume and flow, if it gets too high then you either have to not use the course, have earlier starts, limit the size of the field. It all has to have police clearance I believe as you are racing on public roads, which I think is done at the end of the preceding year when you say what races you are going to run where and when.
Is it more a case that some triathlon bike legs are later in the day for example as they use quieter roads and aren't set courses.