Toyota Repair: 2002toyota camry, timming belt, recommended replacement

Question
my car has 55,000 miles  when should i start being concerned about my timming belt??Also if it should go what would happen if i am driving on highway?What would be the worst scenario  thanks

Answer
If it's a 4 cylinder engine it uses a timing chain which is maintenance free, if it's a V-6 engine the recommended replacement is at 90,000 miles, if the belt should break there is no other damage to the engine but obviously the engine will stop running.