Evacuation you want to prioritized throughput - think of how little road space 100 people in a bus take up vs say 50 cars with 2 people each. Or even 25 cars with 4 people each.

If you have central control you might even be able to get away with changing the rules. i.e. most roads are now one-way leading out of the city. voilà we nearly doubled outbound throughput. Even just for commuting that would be awesome, not that it is happening anytime soon, but one can dream, especially while sitting in gridlock traffic.