Vehicle Chase

[Lloyd Dupont]

Hi all... I am thinking of a chase rule...

I know, I know, there is something in the golden book.... however, hold on with me a moment, I might reuse some of it, but I am trying to come up with my own rule. Just bear with me a moment and tell me what you think.

I think the purpose of the chase is to caught the guy running away, or run away from some pursuer.

My initial approach is each party simply run at their nominal speed and I modify their distance accordingly. If enough space has been acquired, one can hide, cover their track ,etc....

Now my next problem is vehicle speed. I started with each vehicle simply move at its nominal speed, but might be limited by 2 factor, traffic/turn and obstacles. it's where both vehicle handling and driver skill can come in play to get the upper hand with some skill roll, and possibly close or increase the gap.

I was thinking:
traffic: each vehicle drive at traffic speed, roll modified skill roll to go a bit faster than traffic
obstacle: reduce speed by any number between 10% to Handling% of speed. The roll driving skill with usual difficulty modifier to avoid the obstacle. Failure = crash, success = pass the obstacle.

Example 1. case 1 traffic:

Vehicle stat:  SPEED/MOV 200, Handling (i.e. 50%)
Traffic Stat: SPEED: 100, Clutter: 60%

in traffic on run "Diving Skill + Handling - Clutter"%, i case of success they get 10% bonus, i.e. 200x10% = +20 MOV that round, i.e. 120

Example 2: 
Vehicle: SPEED/MOV 200, Handling 50%
Difficult Obstacle, i.e. roll Driving Skill / 2.  Reduce speed as desired between 10% to 50% i.e by 20 to 100. In case of skill failure => crash! for... 1D6 by 30 SPEED?
(or maybe less..limited by the obstacle... have to think some more of it)

What do ya think so far?
Any counter suggestion?

[Atgxtg]

One idea I was toying with was slightly modify RATED SPEED to be the square root of the MOV rate (or 1/10 MOV for values below 100). This is fairly close to the official value for most ground vehicles, scales nicely to give the relative speeds of other vehicles (that is a difference of 30 MOV means a lot at low speeds but not so much at high speeds), and would allow the RATED SPEED figure to be the distance traveled (or number of "zones) moved during a chase (or the difference between the two rated speeds if you just want the relative position).

You could then adjust the SPEED travel by +1 for a special success, +2 for a critical, -1 for a failure (with a second driving roll to avoid a crash), and so forth. 

The goal was to keep things fairly simple while still allowing for relative skill and relative capabilities of the vehicles involved. I did have some ideas for acceleration and such, but they were more like OPTIONAL rules, than necessary ones.

 

Translating this into your examples above...

Vehicle stat:  SPEED/MOV 200, would work out as RATED SPEED 14, with the distance actually traveled based on the success level. Obstacles and clutter could either give a driving penalty or reduce speed to a OBSTACLE SPEED (say half RATED) or both. Maybe a  a large truck on  narrow road might limit vehicles behind it to SPEED 7, but a driving roll at -20% could let a driver slip past for their full RATED SPEED?

 

I think this might work out better for you as you won't have to keep track of exact MOV rates or exact distances. 

[Lloyd Dupont]

Thanks for your comments! 🙂 

Also, 2 days ago, I read the vehicle chase rules a great number of times in a row... and it turns out they do exactly what I was thinking for! 😮 with a few tweaks / simplifications! 😄 

Anyway I like your comment about the square root, their rated speed, while a convenient simplification, left me slightly confused...
And the successes giving +/-1 to ACC. Great idea!

 

Additionally, the foot chase rule are a bit too vague, but I came up with a nice system of my own:

It's also about simply comparing the distance between protagonist. Maybe if the distance is big enough, the guy running away can hide, or the pursuer can take the wrong path. Also, obviously, they might be obstacle along the way that just dead stop the pursuer or the evader, like a wall to climb or a river to swim...

But if it was just a pure running chase:
- each protagonist decide a gait move at x1 (walk), x2 (jog, cost 1 FP), x3 (run cost 2 FP), or x4 (sprint cost 4 FP) (for human, horse would be x1, x2, x4, x8)
- a successful Run skill% check give a +1 multiplier. and an Endurance check give -2FP cost. (-2 for human that are endurance hunter, other animal have -1FP)

and I guess , for simplicity, you just need to track the distance in multiple of 10 / base MOV! 🙂 or "squares"
Haven't tested it.. it's a marathon to run after someone.. but the numbers to juggle are small...

 

Edited March 25, 2021 by Lloyd Dupont

[Atgxtg]

 

 

 

 

12 hours ago, Lloyd Dupont said:

Thanks for your comments! 🙂 

 

Glad to chime in.

 

12 hours ago, Lloyd Dupont said:

Anyway I like your comment about the square root, their rated speed, while a convenient simplification, left me slightly confused...
And the successes giving +/-1 to ACC. Great idea!

 

Let me try to clarify them, maybe then they won't look so great.

As it stands in the BGB vehciles get a MOV score and a RATED SPEED, the latter of which is used in chases. Now there is no offical method of dertemining a vehicles RATED SPEED (or MOV for that matter) and they are just sort of eyeballed. That's fine if you want to use the vehicles listed (well, not really, as water vehicles seem to be as fast as ground vehicles), but what if you want to add addtional vehicles?

My idea was to have RATED SPEED = 1/10th MOV (for vehicles with MOV scores below 100) or RATED SPEED = square root (MOV) for vehicles with a MOV score of 100 or greater. This gives a value that is pretty close to the listed vehicles. 

In practice this meant that a vehicle with a MOV of 100 (RATED SPEED 10) chasing after another car with a MOV of 80 (RATED SPEED 8 ) would move two spaces faster, on average, and either gain two spaces or move two spaces further away each turn. This is where the driving rolls would come in. Higher success levels would net a driver an extra space or two, and failed rolls would slow the vehicle down and require a roll to avoid a crash. Thus the driver in the MOV 80 vehicle has some chance on beater the driver of the faster car.

 

The reasons why I think using RATED SPEED is better than using MOV are:

1. You don't need exact distances and measures. In most cases you don't need to know if a car moved a distance 60 or 66, so it's extra bookkeeping with little reward.
2. Actual speed and distance tends to be less important the faster you are travelling. For instance, if you are in a vehicle with a top speed of 1 mph and I'm in one with a top speed of 2 mph, I have advantage because I have the ability to move twice as fast as you can. But if you in a vehicle with a top speed of  200 mph and I'm I'm in one with a top speed of 201 mph, I have little to no advantage anymore, and it comes down to driving skill. That's what makes a square root progression nice, as you will need a larger difference in MOV rates to get a bonus. Thus an airplane with MOV 450 and one with MOV 475 would both end up with the same RATED SPEED of 21, and the contest would be decided by pilot skill.

 

 

You might want to adapt the chase system from the old James Bond RPG. What it did was set up a number of range bands (Close-Medium-Long-Distant-Extreme, Extreme+1, etc.). Each turn characters in the chase would bid an Ease Factor (read difficulty) to see who went first, and then picked a maneuver such as Pursee/Flee, Quick Turn, Double Back, Force, or Trick (anything other than the previous options).  During a Pursue/Flee maneuver the Quality Rating (read Success Level) would determine how many range bands the vehicle traveled that turn.

Can with high acceleration and handling would be given a bonus to maneuvers, thus a Ferrari is going to blow the doors off of a VW Beetle. There were also some limits of maneuvers based on the relative speed. For instance a man of foot cannot choose the pursue/flee option in a chase against a car as the car is much faster. Instead the man is going to have to try to lose the car by ducking into alleyways (quick turn), reverse direction (double back) or pull off some sort of trick to get away, such as climbing up a fire escape.  

The range bands corresponded to the ranges for missile weapons. This mean that a medium range shot for a pistol was also a medium range shot for a rifle, but this kinda made sense as pistols tend to be easier to use while running or when leaning out a car window. 

 

All in all the system is fairly simple and easy adapt to BRP.

[Lloyd Dupont]

The benefit of rated speed was pretty evident! 🙂 

If you want to keep track of distance travelled, of a MOV 166 vs MOV 154 this is quite tedious... so we simplify to both speed 13 (in virtual pseudo units), easier to manage! ^_^ 
BTW your additional suggestion (linear until 100, square root after is great!)

Your bands suggestion from the James Bond looks pretty similar to what appear in the Vehicle Chase section of the golden book (page 216), me think... or did I miss something?

I was thinking to do like they suggest except... except changing the "Vehicle Range Track" at the bottom a bit (i.e. range 1, 2-3, 4-6, 7-10, 11+)

[Joerg]

While speed and acceleration (and deceleration) are important in a chase, maneuverability, traction and/or turn radius and turnaround speed are integral to chases. Not to mention adverse conditions like oil slicks, ice, water (aquaplaning), smoke/fog/dust, potholes (causing attrition to the vehicles), and use of moving obstacles (aka traffic).

A motorbike will accelerate faster than a decently motorized car, but may lack in top speed, or may be more prone to adverse wind. While not exactly a chase or a race, I had the opportunity to use an unlimited speed low traffic part of German Autobahn to test my car against a motorbike, and while it accelerated to about 110 mph a bit faster than I did, I was able to get a little more top speed and pass the motor cycle. The "chase" ended with the motorcyclist electing to leave for a resting place rather than following me. I managed to make it home in time for the scheduled online meeting without egregiously breaking any legal speed limit...

A hostile chase may see additional maneuvers, like forcing the other vehicle off the street. For any "full contact driving" like giving the chased vehicle a rear bump, the vehicles had better be reinforced, and airbags re-calibrated. It doesn't take much of a bump to your front grill to lose cooling fluid in a moment, or for a side bump to push in the car wing to scrape on the tyre or to hem in the front wheels, limiting steering.

Bodyguards get special training to drive armored cars, both defensively and to create an escape route. I know a retired bodyguard who likes to talk shop every now and then.

I don't think that BRP game values are easier to handle than some ordinary physics. At least over here in Germany, those physics (or at least the results of braking etc. at a few standard speeds, multiplied by the braking distance) are taught as part of getting a driver's license. Then there is the danger of braking harder than the vehicle is really constructed for, when it becomes a case of reaction time and skill to avoid getting into an uncontrollable instability, and managing some instability. Same for maneuvering on slick surfaces - that's skill and reflexes, too. At sufficient speed, first grade dry tarmac can be a slick surface...

Then there is the problem with diminishing returns as your engine is revved up almost all the way. Quite a lot of that is down to engineering, to different gear-switching stratagems, and ultimately to redlining the vehicle - whether traction or engine output or cooling/lubrication, or overheating the brakes. Those can be GMed as narrative trade-offs.

Edited March 26, 2021 by Joerg

[Atgxtg]

On 3/25/2021 at 10:06 PM, Lloyd Dupont said:

BTW your additional suggestion (linear until 100, square root after is great!)

Thanks. I was working on a Vehicle Design System at the time as was trying to come up with a formula that works for all the vehicles listed and this was as close as I could get. In my defense though, some of the listed stats in the BGB don't make a lot of sense. A Battleship is not as fast an an 18-wheeler, for example.

 

On 3/25/2021 at 10:06 PM, Lloyd Dupont said:

Your bands suggestion from the James Bond looks pretty similar to what appear in the Vehicle Chase section of the golden book (page 216), me think... or did I miss something?

It is similar, it's just that Bond gave you more options in a chase other than trying to alter distance. It also could handle different types of vehicles or mixed vehicle chases a bit better. For instance, in a player was driving a Stuz Bearcat and being pursued by a Sophwith Camel.

 

One of the things that was nice about it was that a character had to go last in a chase in order to outrun an oppoent. Otherwise they'd just be a Extreme +1, Extreme +2 etc. This worked out good in play as it meant that if the players wanted to end the chance they would have to let thier opponents act first, and thus possible get closer or even shoot at them.

 

 

[Atgxtg]

On 3/26/2021 at 11:30 AM, Joerg said:

While speed and acceleration (and deceleration) are important in a chase, maneuverability, traction and/or turn radius and turnaround speed are integral to chases. Not to mention adverse conditions like oil slicks, ice, water (aquaplaning), smoke/fog/dust, potholes (causing attrition to the vehicles), and use of moving obstacles (aka traffic).

Yes, that why driver skill and vehicle handle stat should be very important in a chase. It doesn't really matter if your supercar can go 200 mph if you can't control it at that speed.  If the driver can only handle a car going 80, then many of the advantages of the supercar are negated. 

 

That's why I think the number of range bands moved should be based mostly on the driving roll.