>>1131218Basically, if you're not going to have a true metro there's no point in expensive tunnels that are going to multiply the cost of the whole thing despite just a fraction of the system being underground. And it won't significantly improve the service quality either, since most of the line is on the surface anyway. What little speed you gain in the tunnel might even be offset by time lost accessing underground stations.
If you want an LRT, go full surface and give cars a big middle finger. Reduce car lanes, give the trams a ROW and signal priority, and you'll get a service that's just as good.
If you want a Metro, go full Metro with absolute priority on the whole line (either grade separation or standard level crossings, w/e). Doesn't even have to be underground for all of the line. It's more expensive than an LRT but not much more than a Stadtbahn, and you get more than twice the capacity and way better average speed.
LRT is ideal for growing cities, because it can eventually be complemented with a Metro, so you're adding more transport and end up with complementary systems. The idea often cited with Stadtbahn is that it's eventually to be *replaced* by a Metro, which would make the investment less efficient because some of it is being wasted. (Maybe the total cost of the latter idea will be less, but performance and value for money would be much worse.) Also that has happened very rarely if ever, because in Germany for example the Stadtbahn systems already have a problem with paying for tunnel upkeep, so turning it into a full Metro is completely unfeasbile.
All of this doesn't apply to exceptions like Karlsruhe where they would put trams underground because the surface line is totally saturated and thus also causing permeability issues.
