Interesting article in the Liberty Times about the costs of putting Taiwan's urban rail lines underground, versus building elevated lines. The gist is that it cost 3.5 times to move the TRA lines in Taipei underground than it will to elevate the rail line in Taoyuan. The comparison is a little unfair, since construction costs are presumably higher in Taipei, but it's a point I've often wondered about- has burying the TRA line in Taipei really been worth its cost?
Typically the benefits of burying train lines versus elevating them are considered to be the reduction of noise pollution and the increase in light reaching street level; Alon Levy discusses these complaints (and ways to mitigate them) here. To be fair, Alon focuses on two-to-four-track intracity rail, while an elevated TRA line plus HSR would require 6 tracks, though perhaps burying one and elevating the other would have been a possiblity. The problem in Taipei however is that burying the rail lines failed to achieve any benefits over elevation, because once they were buried Taipei simply added an elevated six-lane highway, which produces more pollution than an elevated rail line in addition to having the same problems with noise and blocking light- all for a higher cost.
Zhonghua Rd. is slightly better, but it is still ridiculously wide for an urban road- about 80 meters including the sidewalk, which in a city of too-narrow sidewalks is ironically far too wide and underused as a result. Although not quite a step backward lie Shimin Blvd., it is no better than an elevated 4-track structure. In fact an elevated structure might make the area more pedestrian-friendly by splitting Zhonghua Rd. into two sections.
If it is impossible to only bury some of the tracks or to elevate all of them there are still better ways to use the new space rather than just pavement. Perhaps buildings could have been constructed on the new space along what is now the center of Zhonghua Road, in effect creating two roads with a block in between. New buildings may have also been possible on one side of Shimin Blvd. Adding new buildings would increase the supply of real estate in some of Taipei's most desirable areas, thereby helping combat high costs.
Of course some will argue that the highway was necessary to relieve traffic. This is a fallacy however; Alon Levy's statistical analysis shows that in the US adding highways has no appreciable effect on congestion; and anecdotally New York's experience with highway expansion has shown that adding highways only causes more people to drive while draining mass transit of passengers. Furthermore many trips done by driving could also be done by mass transit. Finally, mass transit is more space-efficient than driving, and if there is one thing everyone should be able to agree on it's that Taipei is short on space. Therefore if extra capacity was really necessary along what's now Shimin Blvd., maybe a better idea would have been building an MRT line (eg, an extension of the Airport Line to Xinyi) rather than an elevated highway, or perhaps speeding up the construction of MRT lines parallel to Shimin (i.e., the Xinyi and Songshan lines) and improvements to the TRA that would add capacity (i.e., signal upgrades and triple-tracking the Nangang-Qidu segment).
In sum, by burying rail lines Taiwan has spent a huge amount of money to benefit drivers. This reflects the auto-oriented viewpoint of the government (and the general population), an attitude which ironically conflicts with other public concerns (lack of space, air pollution, concerns over global warming).