In general, the investment costs in infrastructure could be reduced by avoiding the construction of bridges and tunnels or by shortening the line. Tilting trains might be a less costly alternative than building new tracks with large curve radii. Because an operational model with a tilting train might be to reduce the curve radius of the lines without decreasing speed, thus it will be possible to achieve lower costs by reducing number and length of bridges and tunnels or line length.

This paper compared the construction cost savings for the following two cases when building the 148.65km new electrified double-track line of design speed 250km/h of the Dodam Yeongcheon section of the Jungang line: (1) building a new high-speed line of straightened alignment, and (2) modifying the alignment by reducing the minimum curve radii on the precondition of the tilting trains operation.

Having the horizontal alignment straightened by adopting large curve radii except, the straightened line has a roadbed composition including tunnels of about 51%. On the other hand, the features of the route alternative are: (1) reduced curve lengths of the straightened route by applying the minimum curve radius for tilting trains, (2) construction cost savings by reducing tunnel and bridge lengths, and (3) alignment modification for the segments of the existing line whose roadbed can be utilized to the maximum extent.

The analysis indicated that the final route alternative could save 95.7 million USD or about 2.8% of the total project cost compared with the straightened route. However, the travel time of the route alternative increases by 1.2 minutes from that of the straightened route due to the increased route length, consequently reducing the benefit of passenger travel time savings. Thus, the project cost savings do not necessarily lead to improved economies.

The possible curve radius reduction of the straightened route on the preconditions of the tilting train operation only for the project cost savings should be carefully assessed as it may constrain the future speedup of the route. Hence, the appropriateness assessment of the route alternative based on the precondition of the tilting train operation needs to be reviewed extensively through a cost-benefit analysis in connection with project cost reduction and travel time increases. Furthermore, case studies need to be performed for various topographical conditions such as mountainous, hilly and plane areas in order to see on which topographical conditions the "line flexibility and competitiveness" could be secured for tilting train operation.

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