Catch a bus. Urban buses may not be absolutely the greenest (shoe and peddle power beat them), but they are less polluting and congesting than car and taxi and as more of them shift to less polluting fuels they will only get better.
There was time when the challenge of finding the right bus or even the bus stop to get you where you wanted, and then working out the timetable, might have put you off using public transport altogether, but those days are gone thanks to Google maps on your phone. If you haven’t tried it, just put in your destination and it will give you a route to the bus stop, bus numbers, connections, and times… everything you need everywhere in the world. It’s a green gift.