Hi, thank you so much for your comments, I didn't honestly expect much feedback for this one, if any at all!
I had to tweak the variables a bit to get it balanced well in terms of difficulty spikes. As a result the yellow density starts out quite high but as the loan ticks away their respawn rate slows down, sometimes still a bit too much and it gets quite sparse.
I thought a lot about whether bus fares are acquired on pick up or drop off, in the end I went for the realistic approach, with the thought it might bump the tension when cash is low, i.e. the player needs to desperately make room first before you can gain more fares.
Thanks again!