Whoa, that's unexpected, considering that SimpleAI doesn't do anything fancy when saving.
I loaded your savegames, and this is definitely a game too large for this AI. The game stutters quite hard, probably when the AI is doing the general maintenance loop on its routes. It doesn't stutter that hard with the 2010 savegame, so I assume that it's indeed the AI that causes the stuttering. The 2010 savegame is after the crash, right? Because the AI didn't load anything from that one, and it may explain why the 2010 savegame is easier on my computer.
The AI probably has more than 1000 routes in this game, and it seems that this is simply too much. The only solution to this is to introduce a cap for the number of routes that can be built. It's too bad though that it is quite hard to determine a suitable cap
For the time being, using lower limits for vehicles or a smaller map will probably avoid this problem.
Thanks for reporting!