How to calculate average speed of a roller coaster ...

[Deleted User 13735]

... and thus the actual trip time?

Could this be determined halfway through the ride?
Without knowing the track length and slope/derivatives along the way?
Without a trial run first?
Enquiring minds want to know.

[mduell]

I'm planning so visit Six Flags in the future, I will measure the wind speed while I'm there.

[rollin_eng]

This sounds like an interesting project, please keep us updated with any findings.