Seattle Bike Blog:
When I read this I thought, Oh! Travelers LOVE Link Light Rail. That’s great. But are bikes getting in the way or something? Then you read Sound Transit’s rules, and they say that only four bikes are allowed in a train car at the same time. So if you get on and there were already four there, do you have to get off at the next stop? Is there a fight to the death to see who stays?
In fact, as Seattle Likes Bikes pointed out, it's worse than that: Because bikes can't block the handicapped seating or the aisles, "The only location ... that works is against whichever doors are not going to open at the next station."
This is far from ideal, and seems like allowing the two additional bikes was an arbitrary compromise on Sound Transit's part. Excluding the bicycle storage area, which is now officially shared with luggage, effectively bicycles may only be brought on trains without standing passengers.
Obviously, many transit systems don't accommodate bikes at all, so Sound Transit's decision to include two hooks per train was a big concession. However, once you decide to allow bikes on trains, you've got to come up with a system that works for cyclists.
That means: One that doesn't force bikes to share their only dedicated space with luggage, one that includes enough bike storage space to meet demand, and one that doesn't allow bikes to protrude into the aisles. One example is the Santa Clara Valley Transportation Authority, which allows six bikes on trains—four of them on a bike rack situated in between the two parts of each articulated car. One bonus is that the racks are ground-level, avoiding the need to hang a bike on a hook seven feet in the air.
Side note: As inadequate as Sound Transit's bike-rack system may be, it's at least less complicated than Metro's new plastic three-bike bus racks, which prompted an explanatory flier with no fewer than eight (!) steps (including one with substeps a), b), and c)) to show riders how to load their bikes. This (combined with Metro's 700-word FAQ, which includes handy advice for "small people" who can't manage the heavy racks, AKA women), is a sign that you are Doing it Wrong.)