The Minnesota Department of Public Safety issued an advisory today to motorists urging them to move over and slow down when they come upon emergency vehicles along highways.  The advisory follows a weekend during which four Minnesota State patrol cruisers were struck by other vehicles.  Luckily, no serious injuries were reported.  State law requires motorists to change lanes, or slow down if that's not possible, when they come upon law enforcement vehicles or other emergency responders stopped along roadways with their emergency lights activated.