Several months ago I obtained travel time data for the Downtown Seattle Transit Tunnel (DSTT) which Metro used for performance analysis of the tunnel. With the elimination of the ride free area (RFA), a key component of the bi-partisan compromise to pass the $20 dollar CRC, this information is now much more relevant.
The data includes DSTT travel times during the AM and PM peak for both northbound and southbound travel which was generated using archived data from Metro’s vehicle tracking system. Three data points, fall 2008, fall 2009 and spring 2010 were included. The data, which was provided to me in PDF format, was post processed to create the graphics in the slideshare above (download ppt here).
The first four slides show the percent of peak trips that took equal to or less than that amount of time to travel through the tunnel. So for example in fall 2008 71% of AM southbound trips took less than or equal to 8 minutes, dropping to 56.1% in the fall 2009 and rebounding very slightly to 56.5% in the spring of 2010.
The next four slides compare the data points (fall 2008 to fall 2009 and fall 2009 to spring 2010), which gives you the percent change in trips which took equal to or less than that amount of time to travel through the tunnel. From the pervious example this means 14.9% few trips were completed in less than or equal to 8 minutes between fall 2008 and fall 2009, and .4% more trips were completed in less than or equal to 8 minutes between fall 2009 and spring 2010.
Below are some observations after looking at the data:
- AM service in both directions degraded with the introduction of Link but has not seen additional degradation since then.
- PM service in both directions degraded with the introduction of Link, with this trend continuing in a significant way between the fall 2009 and spring 2010 data points. The spring 2010 service change eliminated the route 194 (4 buses per hour southbound and northbound) and added the 76, 77, 216, 218 and 316 (roughly 10 buses per hour northbound and 7 buses per hour southbound in the PM peak) to the DSTT, increasing the number of buses in the DSTT by 6 buses per hour northbound and 3 buses per hour southbound.
- PM southbound travel is the slowest with only 57% of trips being completed in equal to or less than 9 minutes. Holding all else equal it appears that the addition of Link had roughly the same impact on travel times as the spring 2010 service changes.
- PM northbound travel has seen the most significant degradation of service, partly because it initially had very good performance and partly because of the addition of the out of service security sweep of Link at Westlake. Travel times are now more in line with those of PM southbound travel.
All this data jives with my personal experiences and the internal report Bruce reported on last week. The introduction of Link certainly increased travel times for buses in the DSTT, but the addition of buses in spring 2010 also had a significant impact on PM travel times.