Picking the best pit beef sandwich is like choosing the best crab cake: There are a few requirements, but the rest is left to the intangibles. Bull on the Run, a red portable kitchen on the side of Washington Boulevard, nails the requirements. The pit beef is rare and tender, the horseradish is fresh, and the toppings are varied. Tiger sauce? Pick-a-Pepper sauce? Mustard? Sure. What color? But it’s the intangibles, like the sheer economy of the beef delivery system—park, order at the window, get sandwich in less than a minute, usually, sit on your hood or behind your wheel, and chomp down—that put it over the top. The Bull gets a steady workaday clientele streaming up and down the highway, and it’s open year-round. A pit beef stand serving those steaming sandwiches in the middle of winter? Oh yeah.