Very interesting site, although not all the rail routes listed are actually abandoned per se. For example, I live next to a popular and well-maintained trail that used to be a railway, and the site still lists it as an abandoned rail line.
Notable examples in Seattle include the Burke-Gilman trail, the Sammamish River trail, and close by the Snoqualmie River trail, etc.
ADDED: And as noted elsewhere the railroad or its successors in ownership often still own the right-of-way--however unlikely it would be to revert a popular rail trail to rail use.
Eh? What do you think an ‘abandoned rail line’ is? It’s exactly this.
20 years later, they started the project and the local cycling groups are upset because their path has to be split and rerouted in places to support the new line. Delayed the thing many years as a result.