Running Chases

 John Harper nails it. If you and your players aren't interested in the chase, it could be a single Defy roll. Or you can zoom in with multiple rolls; just make sure to mix up the threats and the stats you're targeting (of course the player's response dictates the Stat, but sometimes you're obviously aiming for one).

There's an obstacle, can you leap it to save time?!
You've stumbled into rough terrain, can you push through?!
Now you're running uphill and it's exhausting, can you endure?!
Oh no, the path forks, can you figure out which way they went?!

That can be one chase sequence, right there. Each result dictates which group gains ground. I love a good chase scene and I like to break them up into mini-encounters; a series of problems to overcome with the goal being your quarry.

Yeah, you can do it that way.

But my advice is to not think of it as a set of obstacles. Just say what's happening and ask what they do. When a move is triggered, roll it. Get out of the "obstacles" and encounters GM-mode.

Describe the environment, say what the monsters do, ask what the players do. Repeat. It's organic and flowing and the GM doesn't have to manage it or make it work out into a "chase sequence" or whatever.

This is slightly unrelated but I was reading Harper's post about "novices worrying about rolling Defy over and over" and I gotta say this is totally true. My players cracked some jokes about overusing the move, so I started just telling the players "Roll +Stat" instead of calling it Defy Danger. The jokes stopped and everyone got back into the game fiction a little more. Presentation makes a big difference. Just like a player should never say "I Hack&Slash," sometimes the GM should just name a Stat and then give them results. I found it helpful... and if you're embroiled in a chase then you might too.

Yeah, that's a good technique.

It also makes the system totally transparent for people and I watched a few epiphanies happen. The whole system is literally just "when you do a thing, roll the most applicable stat" at the core. Some moves happen to be pre-written because they'll come up so often, but every move is, in essence, just rolling the stat that makes the most sense.

I mean, it seems obvious but I've watched multiple people be all "wait a minute... I get it" with big goofy grins suddenly lighting up.

It is obvious, but is not how many systems work, so that is probably why.

Just read through this thread as I found it very interesting. To me, there was one thing that stood out in your discussion, Sarah.

The thing is, sometimes a chase is a flat-out race. :D In the example which cropped up in our game, it was exactly that: there was no danger of getting lost, getting hurt, or getting bogged down; we simply needed to determine whether the PCs were able to catch up with the orcs (and maybe force a fight) before they alerted the giants. As simple as that. It literally was a very long corridor with a door at the end, and the PCs chasing the orcs. The chase *was* the challenge.

To me, given the above description of the situation, there doesn't seem to be a need for more rules to resolve the challenge. While there is certainly some excitement in finding out whether or not the heroes catch the orcs in time, there wasn't much else going on in the fiction to create the excitement you seem to be looking for. Basically, the heroes were running after some enemies in an otherwise featureless hallway. Not much else going on there so I wouldn't exactly count this as a strong example of the adventure-story chase trope. In movies and literature that feature chases, there is almost always a lot more going on then a hallway and the tension of who is the faster sprinter. If that's all there is, then it's not really an exciting chase scene.

So, at the risk of sounding critical, it seems to me like you may have been looking for the rules to help create tension that wasn't actually there. Like you said, the chase was the only challenge; there was only one thing creating a need for dice rolling.

Wanting something a bit more specialized than Defy Danger, I came up with a Move some time ago for PCs running from danger - this might be of interest for chases:

Fly you fools! Characters attempt to run, climb, flee from creatures or other danger. Use roll+con or roll+dex; -1 for clumsy armor, severe wounds or other impairment.  Successfully escape to safe distance on 10+.
7-9 choose 1 in keeping with fiction:
- escape to safe distance but enemy inflicts an Average Wound (3 on d6, 4 on d8, etc) on your backside
- escape to safe distance but drop 1 item; GM decides
- escape to safe distance but damage armor while fleeing (-1 armor)
- escape but tire; suffer -1 forward
Note: enemy may choose to pursue from distance or not, possibly causing hero to “run again!”