I want the vehicles in the inflow to drive constant speed but I want this constant speed to change between episodes (let's make this speed uniformly sampled between 10 m/s and 25 m/s). E.g. in episode #5 all vehicles drive in 12.3 m/s and in episode #6 all vehicles drive in 19.7 m/s.
How can I do that?
Can I do it with only one inflow or do I need an infinite number of inflows, one per speed and change dynamically between them? (which I'm not sure how, anyway)
Yes! It's a little tricky but you can make it work. If you look at the reset method on line 988 of the following file (https://github.com/flow-project/flow/blob/master/flow/envs/bottleneck.py) you can see that what we do is create a new set of inflows and then restart the simulation so that the new set of inflows is active. You should be able to add a similar bit of code to your environment to make it work.