What training is a Boy Scout needs for crowd and traffic control?

Requirement 6 of the Emergency Preparedness merit badge includes:

Do the following:

a. Tell the things a group of Scouts should be prepared to do, the training they need, and the safety precautions they should take for the following emergency services:

1. Crowd and traffic control

You might try the US Military method: Utilize small-scale models which preclude danger to life and limb prior to 'On-The-Job' training.

Of course, I'm an easy target for charts and graphs, but a nice wallmap on a magnetic chalkboard works quite well, also.