Car Wars 5th edition physics problem

[Teclis]

Hi,

I played Car Wars 5th edition for the first time on Saturday. The Three phase system has a problem with the physics in that a car moving at a high velocity can pass a car with a low velocity during its movement phase and then when the lower velocity car moves it can initiate a collision onto the rear of the car with the higher velocity.

In essence you have a slower moving vehicle colliding with a faster moving vehicle that is both in front of it at moving in the same direction, which is impossible.

This could not happen in the Deluxe edition because in each phase a car was only moving one or two inches.

I've been playing Car Wars since I was eight and in my opinion the re-release edition was the best one because it had the deluxe edition phase system with only six phases. The only thing I thought might be better with the 5th edition was the larger scale would be good for hobbyists who prefer building and painting models.

[Magesmiley]

Originally Posted by Teclis

Hi,

I played Car Wars 5th edition for the first time on Saturday. The Three phase system has a problem with the physics in that a car moving at a high velocity can pass a car with a low velocity during its movement phase and then when the lower velocity car moves it can initiate a collision onto the rear of the car with the higher velocity.

In essence you have a slower moving vehicle colliding with a faster moving vehicle that is both in front of it at moving in the same direction, which is impossible.

This could not happen in the Deluxe edition because in each phase a car was only moving one or two inches.

I've been playing Car Wars since I was eight and in my opinion the re-release edition was the best one because it had the deluxe edition phase system with only six phases. The only thing I thought might be better with the 5th edition was the larger scale would be good for hobbyists who prefer building and painting models.

This is a problem with Classic Car Wars as well. It occurs less often there due to cars moving multiple times in a phase less often than in 5th edition. Higher speeds increase the likelihood of it occurring. However, even when cars only move once each phase, it is still possible if the slower car makes a turn into the rear of a car that just passed it.

It's ultimately an artifact of the vehicles alternating movement in time slices. The smaller the slices of time (and movement) the less likely you are to see this problem. Even in video games (which look real enough) the movement is off a tiny bit when a collision occurs - again due to dividing movement up into slices.

As to rules... just treat it as a 0 mph collision (no damage) and move on.

And if you like the size of the 5th edition, you can get the same effect by tripling the scale of the Classic (4th edition) rules.

[Parody]

In CW5 the rulebooks tell you what to do in this situation (under "Rear-End", page 6).

For earlier versions (specifically CWC2.5/UACFH) our group does the same thing, but we allow the faster vehicle to maneuver on the inch(es) they would have lost. I thought the first part came from a ruling in the CWRQ/ODQ, but I can't find it at the moment.

[Anthony]

While it's certainly possible to handle physics problems like that, it generally involves more calculations than most people want to do in a board game (it's really a problem with collision detection, what this actually represents is the high speed vehicle cutting in too soon, resulting in sideswiping the slower vehicle).

[rdeis]

Originally Posted by Magesmiley

This is a problem with Classic Car Wars as well. It occurs less often there due to cars moving multiple times in a phase less often than in 5th edition.

I remember this being a serious problem in play-test, but I thought we fixed it?

In Classic, you break up the motion into alternating inches and it becomes very rare- the faster car has to *allow* the slower car to hit it, which is usually a bad idea so he doesn't.

If he does, the slower car usually has to do something really strange and silly to make the hit rear-end instead of T-bone or sideswipe, which is usually a bad idea so he doesn't either..

[Parody]

Originally Posted by rdeis

I remember this being a serious problem in play-test, but I thought we fixed it?

It happens a few times a year in our group. One example is when initial positioning puts a faster vehicle a bit farther away from an arena feature than a slower one and they both arrive at roughly the same time. The slower vehicle turns in to follow the faster one and shoot at its rear. The difference in speeds usually isn't very much, but it does force the one vehicle to go first regardless of driver skill.

For us tighter arenas like Aladdin's Castle, Macon, or Rainbow Bay are more likely to have it happen, as does Hammer Downs due to the focus on ramps and jumps and the higher divisions involved.

[swordtart]

[QUOTE=Teclis;2100373]Hi,

I played Car Wars 5th edition for the first time on Saturday. The Three phase system has a problem with the physics in that a car moving at a high velocity can pass a car with a low velocity during its movement phase and then when the lower velocity car moves it can initiate a collision onto the rear of the car with the higher velocity.

In essence you have a slower moving vehicle colliding with a faster moving vehicle that is both in front of it at moving in the same direction, which is impossible.
QUOTE]

If you consider the whole movement rather than just the slower vehicle the situation isn't quite as illogical as you summarise. If the faster car passes the slower car then it started behind it. If you consider the whole phase, for the slower car to hit it, the faster car must have misjudged the distance and pulled into a gap that is no longer there when it arrives (not an unheard of situation in real-life).

In cases where this occurs you can simply play the rules as written (and accept that collisions are complex and you shouldn't expect to be able to predict them well enough to plan an effect in advance.

Or you can always break that movement into much smaller "chunks" and iterate it until the collision occurs and use the positions that exist at that point e.g. in classic you have 1 car moving 3" and the other moving 1" divide the phase into 4 sub phases with the first car moving 3/4" and the other moving 1/4" along their pre-selected paths.

This will probably end in the fast vehicle sideswiping the slower vehicle rather than the slow one rear-ending the fast one (which is the likely outcome in the real world).

[helbent4]

Originally Posted by Teclis

Hi,

I played Car Wars 5th edition for the first time on Saturday. The Three phase system has a problem with the physics in that a car moving at a high velocity can pass a car with a low velocity during its movement phase and then when the lower velocity car moves it can initiate a collision onto the rear of the car with the higher velocity.

In essence you have a slower moving vehicle colliding with a faster moving vehicle that is both in front of it at moving in the same direction, which is impossible.

Hi Teclis,

I like 5th edition as well. I am using 1/64 scale vehicles (aka "Hotwheels/Matchbox" scale) but am finding even the 5-phase turns drag somewhat at 3x scale in "open road" scenarios where the combatants are not forced to constantly maneuver and fire. I am running a game with a friend and we are going to switch to 5th ed. 3-phase movement but keep most other rules (primarily for weapons) the same as Classic CW. (Although I do like how it's generally much easier to hit in 5th ed.)

This question was answered previously, so my apologies for going into a little more depth.

Page 6; Rear -End:

"A slower vehicle may not rear-end a faster vehicle. If this appears to occur, the faster vehicle is moved the smallest distance needed to remove the threat. This movement is subtracted from its next phase."

This seems simple enough according to the streamlined nature of 5th edition and works well if the slow vehicle would end its phase in the same spot occupied by the faster vehicle. You may wish to mark the faster vehicle's original starting position somehow to facilitate this, although this might make things a little confusing!

It follows that if the faster vehicle that has been moved in this manner wishes to make a maneuver at the start of its next turn then it can do so from it's original unaltered start point (again, it helps if this spot is marked).

A further suggestion is if the slow vehicle has enough movement to go completely "through" the faster vehicle's position, the slow vehicle simply ignores the presence of the fast vehicle for that move, and only for that move. (It could still theoretically put itself in a position where the faster vehicle is forced to rear-end it at or near the beginning of its next phase, but that's just cheap, not unrealistic!)

Another way around this problem is what I call "convoy" or "pursuit" movement. It's most useful on the open road where all or most vehicles are travelling the same general direction. The lead vehicle on the road moves first regardless of speed, then the next, and so on. This way slower vehicles can usually never rear-end a faster vehicle from behind (as by definition all faster vehicles ahead of it would have moved beyond where it can reach.) It also makes initiative very quick and easy because you can just look at the board and judge who goes next by where they are in relation to everyone.

Tony