I've decided to solve this by 1-starring and no-tipping any driver that fails to yield to a pedestrian, drives in a bike lane, or exceeds the 25mph speed limit at any point in the ride (so, like, all of them), but of course, I take a cab once every three months, so that won't do much.
If we really want to reduce greenhouse gases, a better approach might be:
1. Properly funding the MTA (congestion charging)
2. Widening sidewalks, especially in Midtown
3. Grade-separated and camera-enforced BRT lanes and/or surface rail with signal priority.
4. Proliferation of bike lanes.
5. Charging market rate for all street parking.
Uber and Lyft have have increased car traffic in New York: http://nyc.streetsblog.org/2017/02/27/its-settled-uber-is-ma...