Three alignments were designed per CHSRA Standards according to the Authority’s Basis of Design Policy Document R3.  The alignments have a design speed of 250 mph where feasible.  Where significant topographic constraints occur, the design speed is reduced to the maximum speed possible in the given area.

 

These alignments are designed as double-track the entire way and are fully grade separated.  Double-track spacing standard for high-speed rail is a minimum of 16.5 feet centerline to centerline.  In shared-use corridors, the high-speed rail track centerline must be at least 34 feet from the Metrolink track centerline for operational speeds of 150 mph and lower.  For speeds greater than 150 mph, a minimum of 50 feet is needed between the two tracks.  

 

The minimum corridor width for HSR is 50 feet while 100 feet is desirable according to California High-Speed Train Program EIR/EIS Table 3.0-1.  The minimum horizontal clearance from the track centerline to the face of a fixed object is 10’-4”.  5’-4” is required from track centerline to station platform.

 

The following attenuation time standards are found on page 10-11 of the Authority’s Alignment Design Standards for High-Speed Train Operation.  For speeds greater than 186 mph, desirable attenuation time is to be no less than 3.1 seconds.  At a speed of 250 mph, minimum straight segment length is 1137 feet.  At a speed of 220 mph, minimum straight segment length is 1000 feet.  At a speed of 200 mph, minimum straight segment length is 909 feet.  The shortest straight segment on this alignment where speeds are greater than 186 mph,  is 3500 feet, which is more than desirable.  This extended attenuation time leads to added passenger comfort.

 

For speeds less than 186 mph, desirable attenuation time is to be no less than 2.4 seconds.  At a speed of 186 mph, minimum straight segment length is 655 feet.  At a speed of 150 mph, minimum straight segment length is 528 feet.  At a speed of 125 mph, minimum straight segment length is 200 feet.  The shortest straight segment on this alignment where speeds are less than 186 mph, is 811 feet.  At this point, the train is entering or leaving the station and is traveling less than 50 mph.

The following radii standards are found on page 14 of the Authority’s Alignment Design Standards for High-Speed Train Operation.  Table 3.2.4 provides desirable, minimum, and exceptional radii for design speeds from 125-250 mph.  This alignment includes two curves of radius equal to 30,000 feet.  This is desirable for a design speed of 200 mph.  For a design speed of 220 mph, desirable radius is 35,000 feet.  This is met or exceeded where it is feasible taking into account socioeconomic impact, geography, cost, and constructability.   For speeds less than 125 mph, no specific design criteria are provided and as such, Metrolink standards are used.   Per the SCRRA Design Criteria Manual, the minimum curve radius is 573 feet.

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Alternative IV Geometric Design