Five things to know about what's going on at Daytona International Speedway in advance of the season-opening Daytona 500 on Sunday: --- CRASHING CARS: A seven-car accident in the first full practice of the Daytona 500 sent workers scrambling to repair a section of the grandstand fence and left teams hustling to get backup cars ready. The session ended early after rookie Parker Kligerman's airborne car damaged the fence. Kligerman's car ended up sliding on its roof halfway down the front-stretch at Daytona International Speedway. Joey Logano and Matt Kenseth started the melee when they got together coming out of turn 4 during a drafting session. More...