"There's actually a larger infrastructure for parking than for roadways," said Mikhail Chester, lead author of the study. "This speaks to the sort of hidden infrastructure components that are there to store our vehicles when they're not moving."
As reported in the Knoxville Sentinel:
The group found that parking contributes to greenhouse gases like carbon dioxide, methane and nitrous oxide. In fact, the environmental cost of so many parking spaces can also raise the amount of carbon dioxide emitted per mile by as much as 10 percent for an average car. And, when calculated over the lifetime of a vehicle, the amount of other gases like sulfur dioxide can rise by as much as 25 percent and the amount of soot as much as 90 percent.This matters to bicyclists because the public subsidy for parking encourages more driving, at the expense of other transport modes, including ours. Here's the newspaper's complete article. The authors' own discussion of their work was published in Environmental Research Letters.