Uber data reveals motoring slower than walking in many cities
This is a well-known principle of urban transport. If driving is faster than the alternative transport mode (whether that's public transport, if any, or walking), then at the margins people will switch to driving, but that means more traffic on the road, more congestion, and slower driving speeds. Conversely, if driving is slower than the alternative, then at the margins people will switch away from driving, reducing traffic and increasing driving speeds. So in places where road space is the bottleneck, we expect driving speed to be similar to the speed of the alternative mode. In central London, for example, travel speed has been roughly the same whether you drive or take the Underground, for more than a century.Update since some commenters seem to be having trouble: this process depends on the travellers "at the margin", that is, the people who are most willing to switch modes to reduce their journey time. Thinking in terms of the average or typical traveller is misleading.