Having read the Speedrush TV Season 3 - Day 5 goal 3.1 Drag Race comments by Vampire and dbuck01 as well as further information from AudiR8cer an aracer, I thought I would take some detailed notes.
I forced closed RR3 and then ran the Drag Race a bunch of times.
As observed by others, the lights go green on what seems like even multiples of the interval between red lights. If you start with the first red light and count the red lights 1 and 2 and 3, then keeping that rhythm you will see the green light on either 4, 5 or 6.
The count before the lights go green is a consistent series starting from the first round after you force closed the game.
Rather than resetting the series, Quitting and End Race so as to reload the race continues the series from where you left off, as does winning and moving on to the next opponent.
Once you know the series you can anticipate the green light to get a jump on the bots since they are difficult to beat even with 21 upgrades.
The series may possibly be the same for everyone, but it may be unique to each person.
Even if it isn't the same for everyone, you can establish your series by quitting a bunch of times on the first heat and use that to anticipate the lights to beat the other opponents.
My series was:
4, 5, 6, 6, 6, 5, 4, 5, 4, 5, 6, 4, 4, 5, 5, 4, 6, 6, 5, 5, 6 and 6.
Could someone who has yet to do the drag race please Quit and Retry Round for the heat enough times to see if this pattern is unique to me or common to everyone?
You can Quit before hitting the Launch button to avoid wear and tear on the car. Please force close the app before noting your series so we know it is reset to the beginning of the sequence. If those who haven't yet finished the challenge don't have time for this then maybe some ambitious person who has finished but has a cloud save from before the drag race could go back and test this.
I tried this in the Spider Showdown 5.1 Drag Race under Legend section of the career series and the pattern was the same. I even switched from the McLaren 12C Spider to the Porsche 918 Spyder Concept and the series continued where it had left off.
I also tried it in the Amateur Pure Stock Challenge 6.4 starting with the Silvia and continuing on with the Focus. The series continued where it left off with the 918 and continued through the Silvia and Focus.
This is all rather surprising given how easy it would be to program it to make it actually random (or as random as computer random numbers get).