Metrolink's Long-Promised Tier 4 Not All It's Cracked Up to Be

For years, Metrolink has been attempting to assuage community concerns about persistent air quality problems by touting its long-promised Tier 4 train. These diesel locomotives are purported vaguely to be "up to 85% cleaner". Our group has consistently asked "Cleaner than what?" And hey, anyone remember Volkswagon's amazing clean diesel cars?

Continued delays - technical and otherwise - lead us to further question whether this train is really all that it is touted to be. The recent stalling of a new Tier 4 on its debut press trip only makes us more curious.