Josh Barro provide examples galore of why the answer to that question isn't always yes—where costly rail investment has been to the detriment of existing transit. His column targets proposed projects, such as New York's LaGuardia Airport AirTrain.
Feb 11, 2015 New York Times - The Upshot
Depending upon which Bay Area newspaper you read, the new 3.2-mile Oakland Airport connector, an elevated, driverless tram that takes eight minutes and costs $6, is either a huge success or a $484 million boondoggle. It began service on November 22.
Dec 1, 2014 San Francisco Examiner
BART's Oakland Airport Connector will not look at all like the familiar cable car found across the Bay, but will be propelled by a moving cable similar to the Clay Street Hill RR in S.F. almost 140 years ago. The 3-mile ride to OAK will be 8 minutes.
Jan 3, 2013 San Francisco Chronicle