2018 data will definitely be better to draw from because of everything that has changed since then. In 2011 we had 2 lanes on the (old) Port Mann Bridge, no 96 B-Line in Surrey, an ongoing deadlock on transit funding and in general a different regional landscape - economically and politically. Apart from the fact that trip survey data can get quickly outdated, personally I think basing our transit future/expansion decisions on things like the regional trip diary is a terrible idea. Essentially what you advocate by modelling future transit systems on current trip patterns is planning for today, not tomorrow. I disagree with that. Rather than catering only to existing travel patterns, rapid transit lines
should shift travel patterns. That is how a return on investment is created; that is how you use transit to solve issues in our region.
It's not even hard to see why trips have stayed South-of-Fraser: narrow bridges, inadequate transit and long commute times create challenges for those who commute cross-river. Extending SkyTrain (following the 2012 RRT1A plan) maximizes the 1990s investment we made in the Skybridge. With a significant improvement in cross-river commute times and access, there are a number of issues that could potentially be tackled. As an example, more areas in Surrey (and Langley) become homes for people who need access to the region, creating options for people in a region where housing in general is extremely expensive. Conversely, the South-of-Fraser in general becomes more accessible to those living in the North, with huge benefits to boot. It's not inconceivable that a person living near the Expo Line in Burnaby could be working at Campbell Heights (South Surrey), commuting to the area via SkyTrain to Langley Centre and bus. Last I read there is an
industrial land shortage in our metro, so enabling these outlying areas to actually cater to the region is an important step in addressing this challenge.
It kind of irks me how a lot of people (particularly the LRT-proponent/SkyTrain-opponent crowd) are referring to the regional trip diary and numbers on travel patterns as if it is supposed to be
the benchmark for our big-money transit decisions. Yes, it's a legitimate quantitative observation on how people are getting around and we need these sorts of things in the decision-making process. At the same time, regional trip patterns are so volatile in nature. If the emphasis is being drawn towards trip patterns that could have totally changed by the next year for any number of reasons, and away from other more qualitative observations that really deserve more consideration in the planning process, the result could be a poorly made decision - and a really expensive mistake.
Also, what nname said. Definitely important to distinguish between the trips that could be served by transit, and trips that transit wouldn't really be targeting anyway.