SMA DEPARTING WITH SVFR CLRNC ENTERS CLASS D AIRSPACE WITHOUT CLRNC.

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LEFT TIW SVFR TO THE E. WX IMPROVED TO MVFR BEFORE LEAVING TIW CLASS D AS WAS EXPECTED. FLEW N OF TCM CLASS D; MONITORING SEA VOR WITH DME TO BE SURE TO AVOID SEA CLASS B AIRSPACE. VISUALLY PICKED UP A ROAD WHICH I THOUGHT WAS THE ROAD LEADING TO DEST; 1S0 (PIERCE CO-THUN FIELD) BY TURNING SW. AT THIS TIME I WAS ENCOUNTERING WET SNOW TURNING TO SNOW WITH VISIBILITY TO GND ADEQUATE. CHK FOR WING ICE AND CARB ICE. NEGATIVE FOR BOTH. REMEMBERED TCM CLASS D AND SWITCHED DME TO TCM AND REALIZED I WAS FOLLOWING THE WRONG ROAD; AS DME INDICATED 2.7 E OF TCM. I IMMEDIATELY MADE A CORRECTION TO AN E HDG DIRECT TO 1S0. WX AT 1S0 WAS VFR/MVFR. SIT COULD HAVE BEEN AVOIDED IF I HAD MONITORED TCM VOR AND FLOWN AN ARC TO 1S0. 20/20 HINDSIGHT IS TREMENDOUS AFTER THE FACT. I CONSIDERED FLYING IFR BUT DECIDED NOT TO BECAUSE THERE IS NO APCH TO 1S0 AND MVA MAY NOT BE LOW ENOUGH TO GET VISUAL. ALSO THE ICING LEVEL WAS RPTED AT 3000 FT MSL AND DID NOT WANT TO DEAL WITH ICE IN THIS ACFT AS IT HAS NO DE/ANTI-ICE PROTECTION.