A towable crash-attenuating vehicle is shown having a frame; at least two axles coupled to the frame, each of the axles having wheels attached thereto; a T-shaped ballast coupled to the frame, and oriented such that the weight of the ballast is biased toward the front end of the frame; deflection shields coupled to the right and left sides of the frame, wherein the deflection shields cover the frame and a majority of the wheels on each side of the vehicle; a tow connection coupled to the front of the frame, pivotable from a deployed state to an undeployed state; an impact attenuator coupled to the rear of the frame; wherein the vehicle is provided with a brake system, and wherein said brake system may be locked and unlocked and wherein the vehicle is provided with an on-board mechanism for locking and unlocking the brake system.