The busway is Jakarta's first stab at a public mass transit system. We only use it for long trips, but when you have to get across town it's a pretty good option -- cheaper and faster than a taxi.
I had never heard of a busway before I came here. Apparently they borrowed the idea from Bogota, Colombia. Basically, it's a bus system with its own lanes.
In the photo above, we're looking straight ahead from a bus down a blissfully empty lane, and the traffic is backed up in the two lanes to the left.
The crucial element is the little concrete barrier running down the left side of the bus lane. Some sections of the busway don't have that, so other drivers ignore the rules and weave in and out of the bus lane, and then the whole advantage is lost.
The busway has dedicated stations with turnstiles; you can't just flag down a bus. In that sense it's more like a subway or light rail system.
They're building busways all over Jakarta now, which makes the traffic and pollution even worse, plus they're tearing down trees along the roads. Hopefully it'll be worth it in the end.