Here is some advice, offered by the Utah DMV, on the proper way to park on a hill. You may want to pass this along to your fleet drivers as a friendly reminder.
1. If you are parking uphill beside a curb, turn your front wheels away from the curb and let your vehicle roll back so that the front tire touches the curb.
2. Never leave your vehicle until you have set the emergency brake, stopped the motor, removed the ignition key and locked the doors.
3. Pull as far off the road as reasonable to park. If parking next to a curb, the back wheel of your car must be no further than 12 inches away from the curb.
4. If your parking would block the flow of traffic, find another place to park.
5. If you are parked outside a business or residential area, your vehicle must be clearly seen from 200 feet in each direction.
6. A courteous driver never parks too close to another car. Parking too close to another car could result in damage to your vehicle.