The pilot stated that he visually confirmed there were 52 gallons of fuel onboard and that both fuel caps were secure to their respective fuel port during his preflight inspection of the airplane. The pilot then departed on the approximate 1 hour and 15-minute flight. While en route, the “low fuel light” flickered on and off. The pilot noted the fuel gauge was reading half full, and he continued with the flight. When the airplane was about 8 minutes from the destination airport, and after descending to traffic pattern altitude, the engine stopped producing power. The pilot was unable to restart the engine and made a forced landing to a highway. The airplane impacted a jersey barrier during the landing, which resulted in substantial damage to the airframe. Federal Aviation Administration inspectors examined the airplane accident site and observed that the left wing fuel cap was missing and blue fuel stains were evident on the wing aft of the fuel cap that extended to the trailing edge of the flap. Recovery personnel also reported that both fuel tanks were empty when the wings were removed for transport. The missing fuel cap was not located. Based on this information, it is likely that the pilot did not properly secure the left fuel cap during the preflight inspection, and that during the flight it separated from the airplane. The remaining fuel was siphoned from the fuel tanks through the open fuel port, resulting in fuel exhaustion, and the total loss of engine power.