This is something I've built today after realising this could be used in a half-track:
The braked differential steering is a steering system that was widely used in tanks. The idea is that we lock one output drive from differential and thus all power goes to the other side.
In theory it is simple, but with no dedicated brakes in Lego Technic it gets complicated. It was often used with differential lock for driving straight though, which complicates such mechanism even more in Technic model.
The drive input is in a poor position for the tank - I'll probably have to figure out how to connect the drive from the other side if I want to use it in a tank build, but it's not an easy task. It might be just in the right spot for the halftrack model though.