The 12/12/13 post explained why Sound Transit should abandon their Prop 1 light rail extensions. This post provides more details about the light rail operating costs behind this conclusion.
Each light rail car costs about $25 per mile (excluding depreciation) to operate. The 13-mile extension to Lynnwood will cost Sound Transit $1300 per round trip for a 2-car train. With 4-minute headways between trains, the 15 trains per hour will cost nearly $20,000 an hour. Of the 20 hours of light rail operation every day, presumbably about 8 hrs would be with 4 min. headways and 12 hours with 8 minutes between trains. Thus it would cost $320,000 per day for ST to operate 2 car trains to Lynnwood. Even if they managed to get the highly unlikely 15,000 riders per day ST promised it would cost more than $21.00 per rider in each direction.
Its not clear whether the Sound Transit University Station has provisions that allow trains to return to Seattle rather than continuing to Lynnwood. If they do, it makes their decision not to locate a T/C at the University even more absurd. Thousands of 520 BRT commuters in both directions could use the interface at the T/C for light rail trips to and from Seattle.
Light rails problem in Seattle is that 2-car trains every 4 minutes through the tunnel to Lynnwood limits East Link cross-lake service to 2-car trains every 8 min. during the peak hours and 16 minutes off peak. The resulting peak capacity of 2220 riders per hour (rph) (1110 rph off peak) with 148 riders-per-car is a tiny fraction of the 12,000 rph ST promised for East Link in each direction. They could double the capacity by going to 4-car trains and still fall far short of promised level. Presumably, operating costs for 4-car trains would require East Link trains not continue to Lynnwood.
The Federal Way extension has about the same operating cost per trip problem as Lynnwood. Since only half the trains go there the daily operating costs are halved. However the costs per rider will probably exceed those for Lynnwood because of the far fewer riders from Federal Way.
In conclusion the only way light rail can be viable in Seattle is to limit light rail to a University to SeaTac “trunk line” and add a T/C at the University Station. The University T/C would add sufficient riders to justify the 4-car train operation needed to at least approach the 110,000 daily riders Sound Transit initially promised voters. Stopping East Link would end the idiocy of Sound Transit confiscating the I-90 Bridge center roadway capable of 1000 buses an hour for a 2-car train running every 8 minutes.
The bottom line is Sound Transit, in implementing the Prop 1 extensions will spend $20 billion over the next ten years creating a light rail system that will be too expensive to operate. Doing so with the state's current inability to find the funds to alleviate the 4th worst congestion in the country is insane.