Yesterday morning a driver for an appliance company got out of his truck on East 50th Street without locking the air brake, sending the 24-foot box truck rolling east across Lexington Avenue. Fortunately, it crossed the avenue just as the traffic light turned green, then crashed into some construction scaffolding without injuring a single soul. Kirk, the 25-year-old driver who would only give the Daily News his first name, explalins, "I thought someone stole it. I was shocked to see no one in it when I opened the door." Bystander Tony Wood says the truck narrowly missed "a lady trying to cross the street but she stepped back." And subcontractor Alan Cheung tells the News, "I'm still shocked. This is my seventh cigarette this morning. I haven't been able to get in work mode since." (We'll have to remember that excuse.) Police did not charge Kirk, who insists he put the vehicle in park before jumping out. Regardless, it's hard to read about this harrowing incident without recalling the horrible crash in Chinatown in January, when a minivan jumped a curb, killing two children and injuring 17.