A and D are great, but do they really require loops are there not streetcars you can operate from one end both ways or have a operators spot on either side?
I'd like to see A turn south to MRU and D go all the way to Britannia. But as has been said buses are much cheaper. Just make these frequent bus routes.
OR... Have the D route going down 4th and into Mission and then into the barley belt east of Macleod.
The thing with operating a out-and-back service where the operator switches ends is that you then absolutely need at least the turnaround area to be dedicated to transit (since it has two-way transit service in a single lane, including a couple of minutes with the streetcar stopped while the driver switches ends). You can't do streetcar-in-mixed-traffic, which is cheaper in terms of political capital.
The D route makes more sense going down Mission Road; there's no point in increasing transit service down a corridor that already has decent transit service and that isn't going to intensify beyond single-family detached mansions, which is basically everything on Elbow between 26th and 48th avenues.
The thing with circulators -- by which I mean relatively short transit routes that cover dense areas -- is that they are competing with walking, which means that for the general public they only work with very high frequencies. From 4th St & 17th Ave, it's 700m to Tomkins Park/Best Buy, 800m to the Vic Park LRT, or to Earl's in Mission and 1000m to 7th Ave LRT. That range of walk is 10-15 minutes, depending on speed and how you hit the lights. If you take a circulator, it'll take 3-5 minutes to travel. If it runs every 20 minutes (which is often MAX frequency), then most of the time, you would be faster to walk. Even if it runs every 10 minutes, if the streetcar just left you'll be able to walk to a destination 12 or 13 minutes away faster than the streetcar can get you there.
And that's without considering a fare. If you're using a circulator to connect to transit, then the marginal fare is free; you'd pay anyways. But if you are paying money for the circulator, are you going to pay $4 to save two minutes? Unlikely. Here's a figure based on a toy model; considering walk distances from 700-1000m at speeds from 3.5 to 4.8 km/h and ride times of 3-5 minutes, with $20 per hour value of time. It's not perfect, but a general guideline.
If you run them frequently and offer a cheap fare, you can attract people to a circulator; a good example is the
DC Circulator, which attracts 1.5M riders a year across 6 routes; the buses run every 10 minutes and the fare is $1. But the routes are longer than the A or D above; DC has a large area built up to a reasonably high density (due to the lack of skyscrapers), and the subsidy is still $3-4 per rider. And the Free Fare Zone here attracts ~6 times as many riders.
Because they only work with high frequency and low cost, circulators are an expensive game for a transit agency to operate. And to some degree, you're replacing walking with motor vehicle usage. Their main benefit in general is as a tool to encourage development.
Over longer distances, you are no longer competing with walking. Here's the same figure with the distances (walk and ride times) doubled to represent 1.5-2km distances:
At this point, though, transit starts to compete with the car.
