Ambulances have chains attached beneath them to ensure the vehicles are constantly grounded. ... As the ambulance comes into contact with these electrons, static-electricity risk increases. By suspending chains under the vehicle, the charged electrons move to the less-charged ground below.

Why do emergency vehicles have chains?

The system makes the chains spin in front of the wheels. When the tires rotate, they catch the chains, greatly improving traction on icy or slick roads. ... And while these types of vehicles are often heavy and more easily driven in snow, the chains can assist when they need to drive uphill.

What are the chains for under a bus?

The chains are designed to provide traction on snow-packed and icy roads and struggle to function in thick snow, Snoozy said. If a bus is stopped at the top of a snowy hill, the chains will stop moving and won't provide the traction needed to help the bus keep going.