Uhhh... Chase Sequences?

There have been a couple times in my campaign that the players have gotten into a chase sequence, and I don't really know how to run them. What are the mechanics of that?

There are some fairly complex rules for it in chapter 3 of the Dungeon Master's Guide (see here).

I have to say that, while I've never run the DMG chase rules, they don't look very appealing to me.

If I were running a chase, I'd model it on the lines of a 4e skill challenge, where the player(s) have to make X successful skill checks before they get Y failures. (Figuring out X, Y, and the general difficulty of the checks is important but I'm not going to address it here.)

(Whether I'd run it as a group action, or a bunch of individual challenges being run in parallel depends on circumstance -- if everybody's running, or riding horses, then it makes more sense to run it as multiple parallel challenges, although that's way more complicated. If they're in a vehicle, it makes the most sense to run it as a group check, since they can't easily get separated.)

This assumes that one side isn't significantly faster than the other, and that nobody can just break the premise by teleporting or the like. If those are true then you don't actually have a chase.

The nature of the checks will depend on the obstacles presented -- it shouldn't just be athletics. Appropriate spells and special abilities can be used to simply succeed on a check -- if the obstacle is jumping a river, and you can fly, you don't need to roll. Other abilities may well provide advantage on checks.

And it's not necessarily "the GM presents a list of obstacles in sequence". The players, especially if they're the ones being chased, can actively attempt to change their fates by making risky maneuvers and creating obstacles.

Significantly, the other side should not be rolling -- it's the players' game, and they should win on lose on their own abilities and cleverness.

A couple of thoughts:

One thing to do if you want to have some options to lay before them is allow them to Dash for advantage on rolls for physical things like burst of speed, pushing through crowds, etc.- basically anything physical. But limit it to something like 1+CON mod times. Gives them a way to either make an early push or try to make up ground after failed rolls, and allows build choices to affect the outcome outside of the roll mods.

On the other end, do you really want the chases to potentially fail, or are you just looking to spruce up the scene before they hit the next plot point? If you prefer to keep the plot moving rather than potentially have avenues of progression come up short, then you can still let players do some improv rolling for the chase, but stage manage it so the quarry will end up caught in the end. If your group likes coming up with actions to roll for it can be a fun time, and you don't have to come up with secondary lines of progression if the dice decide to sandbag the group.

One thing I would definitely do if you use the official rules is to not say "X obstacle blocks your path; make X skill check." I've been subjected to a chase ran like that, and it is NOT fun. Instead, it should be "X obstacle blocks your path, how do you want to solve it?" Also, even if you use the DMG's random obstacles, make sure they affect all creatures behind the first affected one. It's really weird when a bunch of people are chasing each other but only one has to deal with the broken-down wagon blocking the road.

The counterpoint to the bit about making everyone roll is that unless you’re aggregating the results, mass skill checks can easily result in bumping off several party members, simply due to dice variance. Abstracting it out so everyone without STR and/or Athletics isn’t likely to get stopped at the first hurdle keeps the whole party engaged.