Mass transit subsidies are more obvious, but private transport is massively subsidised by the government and community. Roads, highways, bridges, tunnels, etc, etc. Hundreds of billions is spent on road infrastructure. (Some overlap here, but the great proportion is used by private cars.)
Hundreds of billions on health costs -- car accidents, air pollution.
Hundreds of billions in wars to secure access to automobile fuel.
If all the costs of private urban road transport were added up, maybe we could see which forms of transport really cost more.