Often the measurement of the sanity of an approach is "What would happen if everyone did what you are doing?"

Well - if everyone rode a bike instead of driving a car - we would be saving a lot of gas. They choose to use a vehicle requiring gas. If you slowed me down on a bike - well, I might consume some more food, but that would be it. The key fact is that bike lanes are not provided for you. The people who are wasting the fuel are the drivers - and the city planners. If you don't ride your bike, there is no hope of ever getting the bike lanes. Chicken and egg scenario.

I wouldn't sweat it - you are doing your part - and you are not guilty for them not doing theirs. If you are concerned about your environmental impact - I believe you are doing the right thing.

Interesting observation though.