Here are ways to keep small passengers in line and safe in a crowded car, from Dorothy Singer, a Yale University developmental psychologist:

- Establish rules of the road. Before the first car-pool run, get together with participating parents and discuss basics, such as where the kids should meet the driver of the day, whether there should be a no-food law, and guidelines for staying seated until the car stops.- Strap them in. Place infants in rear-facing safety seats until they're age 1 and weigh at least 20 pounds; place kids 1 and older weighing 21 to 40 pounds in forward-facing seats; and put those from 41 to around 80 pounds in booster seats. Children over 80 pounds can use the car's safety belt. The safest place for all kids is the back seat.

- Keep diversions handy. Take turns deciding what music or stories on tape will be played and make it clear that car-friendly toys, such as felt boards and puppets, are to be shared.

- Practice crowd control. If the kids get too rowdy or begin fighting, give them one warning and don't hesitate to pull over to a safe place until they quiet down. "Kids don't like to sit still," says Singer, "so they'll put a lot of pressure on each other to behave."