The Arrowcar was once the main transportation of Green Arrow and Speedy. It was yellow and came equipped with an ejector seat and was able to shoot Net Arrows from the headlights. During the pre-Crisis universe the Arrowcar was sold at an auction for $100,000. It was later destroyed by a Grenade Arrow. (World's Finest Comics #254)
The car was seen being thrown at Green Arrow by Solomon Grundy during the Archer's Quest story arc after Speedy (now Arsenal) and Green Arrow went hunting for all of Green Arrow's most valuable possessions. It was also seen later when Ollie tells a story to Mia about the Arrowcar, because she sees there is someone auctioning off the Arrowcar online.
Batman buys it for Ollie, but in the end Ollie blows it up, destroying the Arrowcar forever. These are conflicting in continuity, but it hasn't been clarified which of these is the actual fate of the Arrowcar.