There are a couple of factors that might drive some of the decrease in driving.
The decrease is happening in 5 Canadian cities. In Canada the price of gas is near $5 a gallon. Sometimes more. These cities tend to be more densely populate than US cities, so traffic congestion is nasty. Canadians own far fewer cars per capita than Americans (
Canada = 620 US=868 per 1000 people). Canadians pay higher taxes than Americans and would seem to have less disposable income to throw for gasoline.
Nonetheless, there is a lot of evidence than something similar is happening in the US. I can give only personal evidence. I have 3 children, 2 of whom have DLs and cars. One lives in the Toronto area and (as much as possible) beats traffic by taking the train to work. The other is moving to downtown Des Moines so he can walk to work.
To the point ArtKansas made, there is also a lot of evidence that the trend is starting. City governments across North American understand the urgent need to reduce congestion in their centers. There is a strong will in most cities (at least in the north half of the US...) to support transportation alternatives.
I say the writing is on the wall... You can argue thatn 1.7% is a significant figure or not. I don't think the statistic matters.
It's happening.