DoorDash is adding restaurant reservations and robot deliveries to its menu in some U.S. markets. The San Francisco-based company, already the largest U.S. delivery provider, announced its expansion plans Tuesday, saying it wants to bring even more business to the merchants it works with. DoorDash said it will soon begin offering restaurant reservations in its app in New York and Miami. Other cities will follow later this year. The company also plans to begin offering deliveries in the Phoenix area with its own autonomous robot, called Dot. DoorDash said the robot, which is 4.5-feet tall, can travel up to 20 miles per hour on streets, sidewalks and driveways.