Something that comes up occasionally on comment sections that I see is the idea of extending the CityCat upriver from UQ. I suspect it’s not justifiable for journeys to (or past) the city but it might be worthwhile for more local trips.

Where

We’ll consider going as far as Indooroopilly in this analysis. It’s almost the same distance from UQ as UQ is from North Quay in the CBD (10km), and past it there’s comparatively little development on the northern bank of the river.

There are a number of potential wharf locations:

At Indooroopilly, the obvious place is at the old barracks site just downstream of all the bridges there.
A stop is possible at Graceville along Nadine St, serving the small portion of that suburb outside easy walking distance to the train station.
A stop at Tennyson next to the tennis centre seems to be highly desirable and should be part of any assumed service pattern. Tennyson would be just under 6km upriver of UQ.
Depending on how far west the Tennyson stop is, an additional stop at Yeronga (literally at Yeronga St) might be possible. This is the location with the shortest possible walk to a Beenleigh-line train station.
A stop on the Yeronga peninsula seems obvious and at least one is necessary, but the question is where to put it. A location at the end of Anita St seems reasonable. It’s under a kilometre to most of the peninsula’s housing (and the distance to the school is about the same as from the school to Yeronga train station).
A stop at Long Pocket is intriguing, but current levels of development are fairly minimal. A proper public path along the river edge of the golf links up to St Lucia would probably be more worthwhile, especially with…
A St Lucia stop at the Esplanade park provides a possible cross-river connection.
A second, northern Yeronga-peninsula stop is another possibility. It wouldn’t provide access so much for Yeronga specifically, as be the most convenient place for a stop serving part of Fairfield.
A Fairfield stop doesn’t seem particularly necessary. The 196 bus and the Eleanor Schonell Bridge are both quite close. In particular, a northern-Yeronga stop is almost a Fairfield stop anyway depending on how far west it is.

This presents us with a problem. If both the northern-bank stops are marginal at best, then is there really any cross-river demand here other than to UQ, or for that matter, in most places? West End to UQ and Bulimba to Teneriffe are busy, but the Norman Park to New Farm ferry only had a few passengers per service according to patronage data and the Kangaroo Point to City ones aren’t much better. Every other suburb-to-suburb cross-river pair on the CityCat is only a small fraction of patronage; it’s mostly to the CBD stops and to South Bank.

And if there’s minimal cross-river demand then why not just improve the buses? Extend the 196 into Yeronga and put some sort of frequentish service through Tennyson?

Timing

The maximum CityCat speed I’ve seen quoted is 25 knots, which equates to just over 45 km/h. As the river is narrower and shallower and its banks are more fragile upriver, it seems likely that we can take this as a better-than-best case speed. Additionally, stop time must be accounted for. Comparing a timetable from 2005 (without Milton) and one from 2021, it takes three minutes longer to the time taken to go from Regatta to North Quay. But looking at the timetable further downriver it’s clearly less than three minutes per stop as some stops are only three minutes apart! Perhaps the Go-Between and Kurilpa bridges have also slowed things down.

With this as a basis, I estimate a absolute-best-case base time of 15 minutes from Indooroopilly to UQ, with no stops in between. To this, I add three minutes for each of our two guaranteed stops, at Tennyson and Anita St Yeronga.

Timing comparisons

Riverine transport isn’t necessarily uncompetitive but for longer-distance CBD commutes it is.

UQ to North Quay is 22 minutes by CityCat. 30 minutes to QUT, 40 to Riverside.
UQ Lakes to King George Square is about 18 minutes by 66 bus
Indooroopilly to Central by train is about 14 minutes
Indooroopilly (Lambert/Central) to UQ (Chancellors Place) is about 18 minutes by the 428 bus
Indooroopilly to UQ Lakes is an estimated 21 minutes MINIMUM by CityCat
- therefore, the primary value of CityCat extension is non-city trips
It’s about 20-25 minutes from Fairfield shops to the city by the 196 bus (off peak), and 17 from Fairfield station to Central by train
The 105 takes 8 minutes to get from Orsova Rd @ Brisbane Corso (NE point on the peninsula) to its stop outside Fairfield shops. Presumably a 196 extension would take a similar amount of time - no more than 10 minutes at least from the end of the peninsula to the shops and then its existing route to the city. Then again, nobody down the end of the peninsula wants a bus layover outside their house. Imagine how bad a ferry terminal would be! On the third hand, maybe people would be more willing to accept a ferry.