How far is your total commute including the 9 miles? I'd be tempted to do the same as you with a long commute. Are the alternative streets that are practical for you to ride? Within 1 or 2 blocks of my main route (that I don't take) I found a "bike route" where you rarely encounter any cars. Trade off: too many stops. Since my total commute is short (3.5 mi), that's OK.