[vl]

Yep, it's unclear how it's measured and if the metric applied correctly. For example, in Seattle traffic jams get only worse over years. Clearly it hasn't "peaked". Yet map from the article shows that it peaked in the Washington state as a whole.

[nulltype]

Hilariously, the graph in the article is "Vehicle Miles Travelled" not "Hours spent in vehicle" which could be increasing while the other decreases.

[tsotha]

Yeah, something like "average highway speed" would be a better metric.