A tidbit that Martin tangentially covered last week is the the current operations plan for Link once ST2 is fully built out. The North Corridor Alternative Analysis includes a discussion of the current operations plan. It identifies two lines, both operating at 8-minute peak headways, for a combined headway of 4-minutes on the common segment from the International District Station to Lynnwood.
Figure S-10 illustrates the planned light rail system configuration once extensions are completed east to Overlake in Redmond, south to South 200th Street in SeaTac, and north to Lynnwood. As can be seen in Figure S-10, the system will operate with two lines, one from Lynnwood to South 200th Street and one from Lynnwood to Overlake. Both lines will operate at 8-minute peak-period headways resulting in 4-minute peak headways between the junction at the south end of the Seattle CBD and Lynnwood, and requiring every train operating in the system to traverse the segment between Northgate and Lynnwood. Ridership forecasting indicates that this level of service, at least south of Lynnwood, will be needed to accommodate forecasted demand in the future. As a result, any delays incurred in the segment between Northgate and Lynnwood will affect the operation of the entire light rail system. This problem becomes worse when the system is eventually built north to Everett, south to Tacoma, and east to downtown Redmond.
Previous planning documents from the Roads and Transit package assumed three 9-minute headway lines resulting in 3-minute headways on the common segment during peak periods, with two 10-minute headway lines during non-peak periods.
Line 1: Northgate to Tacoma Dome Station. 4-car trains running every 9 minutes peak, 10 minutes off-peak.
Line 2: 164th SW/Ash Way to Kent-Des Moines Road. 3-car trains running every 9 minutes peak only.
Line 3: 164th SW/Ash Way to Overlake Transit Center. 4-car trains running every 9 minutes peak, 10 minutes off- peak.
This change results in less frequent service in the overlapping segments by 1-minute, but more frequent service on the non-overlapping segments by 1-minute. At 4-minute headways additional service can be added if additional capacity is needed, with fewer impacts on reliability. This change also simplify operations for ST because trains go out of service only at the end terminals, not midway along the segment north and south of Seattle. This benefits users as well and eliminates confusion between peak and off-peak operating patters.