Monday, 13 August 2012

A Simple Chase Rule

Following on the previous post about random movement rates and chases, here's the simplest chase rule I can come up with:

Just before moving, a character may choose to give up its regular movement rate and instead move d6 for every 3 points of movement, plus 1 for every leftover point. A movement rate of 12 becomes 4d6, for example, and a move of 10 becomes 3d6+1. This move is rerolled on every round it is used.

Cue "Yakety Sax."
This does a number of things.

1. It makes chases exciting in a simple and traditional way.
2. In normal tactical combat movement, there is seldom going to be a reason to delay the game by rolling movement instead of using the reliable rate. As I noted last time, the normal move rate usually will be enough to do whatever maneuvering is needed once sides have closed. If that's so, then you don't want to take the chance of a low roll ruining it.
3. The dice will normally only be used if speed is of the essence - charging missile weapons, racing an enemy to get to a switch, or just plain chases. Why? Because the average roll of a d6 is 3.5, giving a variable but overall half-point advantage over a plain predictable 3.
4. It represents switching from a more cautious to a more risky mode of movement. Good and bad rolls can  be visualized as bursts of speed or accidents.
5. It slots easily into any number of combat rules sequences by offering an option for movement, whenever and however that happens.
6. It reflects the advantage of a large pursuing party; each round, the more figures you have, the more likely someone will roll high and catch up. Outpacing a horde of 6-move kobolds with your 9-move party is no longer such a done deal! At the same time, if this gives too much unrealistic advantage to an unruly mob, you can just say (as my rules do) that you need to spend 3 movement points in order to pass through a slower figure in front. 

As simple as it is, this rule is missing a couple of things. One is the possibility for character stats and terrain to regulate such things as dodging obstacles and getting tired. These I'll cover next post.

Another is a protocol for ending the chase. With perfect visibility ahead, a chase can continue until the pursuing side catches up or gives up. If a chase is taking place across terrain already mapped by the DM - for example, a dungeon or a well-developed city - then visibility is easy to determine. Otherwise, visibility can be determined generically - 10' in thick fog, 20' in twisty city streets, 30' in deep woods, and so on.

When the chasers lose sight of their quarry and there is more than one way to go, they need to decide whether to split up, continue along one way at the risk of being entirely wrong, or give up. Those being pursued, once the chasers lose sight of them, also have the well-known cinematic option of finding some place to hide and waiting as the chase goes by. 

To guard against this, the more intelligent kind of pursuers, if numerous,  will need to leave behind a searcher each round. Somehow, they never seem to do that in the movies ...


  1. For a bit less math: how about only ONE increment of 3 movement points gets converted to 1d6 instead? That actually results in more variation than rolling 3d6 or 4d6. However, it eliminates extreme results.

  2. I like it. Just needs some Dex factored in for speed and agility and Con for stamina.

  3. A few ideas: Difficult terrain could be handled by forcing the PCs (or NPCs) to reroll their highest dice. Some monsters, like spiders, may be able to ignore this.

    PCs can also reroll any die that is equal or less than their Dex mod. Rangers (or those skilled in wilderness) can reroll dice less than or equal to INT mod.

    Also, I'm not sure how to handle it, but letting a mob of monsters roll different dice will result in some getting high numbers (and thus moving faster) but that will mean the monsters will be split up into multiple smaller groups. The PCs could then fight these small groups one at a time and possibly defeat a large group that way.

  4. I agree that the game would benefit from random movement, especially at the larger, abstracted scales. I find I fudge it in chase scenes, maybe by rolling CON/Endurance checks to keep going. In versions of D&D with specific Evasion % chances I can use that.

  5. I definitely think that any rule that spreads out pursuers and pursued so that the leading element of one catches the trailing element of the other is a good idea, both realistic and fun.

    1. So, thinking about it, next time I have a chase scene in Labyrinth Lord I shall use this rule! :)

  6. I used this yesterday. One player character fighter was wearing plate mail and was trying to run away from a shark man in a space suit. 1d6 vs 2d6, the first to reach 20 would get their way, I said. It was no contest: sharkman cornered lone fighter in no time...

  7. I think a good chase system has yet to be made. For me, it would require a fast and easy to use but also detailed terrain generation system.

    Think of that like a conveyor belt. The terrain would need to be generated as the chase extends into it. Of course the terrain would also need to match existing DM maps of the area, or at least not contradict them.

    Finally the details created would need to provide a combination of obstacles and choices. Sometimes an obstacle is just and obstacle - a fence, a gap between roofs.

    The fun comes when the escapee can make a choice between two routes. Then they can make a risk-analysis over their chances of making it over an obstacle vs their pursuers chance. This way fast runners will go for flat routes whilst good climbers head up.

    Throw in a few surprises like applecarts and men carrying sheets of glass. I was working on a few prototypes but nothing satisfying yet.