Highway Traffic

[Asmor]

One of my players really likes cars a lot, so I'm planning on having a high speed chase soon (most likely in the next session, Thursday) on a heavily trafficked highway. I plan to be using a system where every square represents the space one car might take up on a highway (so a three lane highway will be three squares wide and each square will be roughly 15' long or so).

I'm gonna be using a table to randomly generate the traffic, like so:

Traffic pattern
1d20 X=vehicle
---------------
1-2     | |
2-4    X|X|X
5-6    X| |
7-8    X|X|
9-11   X| |X
12-14   |X|X
15-17   |X|
18-20   | |X

Vehicle type
1d20
-------------
1     2 Motorcycles
2     Huge truck (takes up 2 extra squares forward)
3-4   Motorcycle
5-6   Slow car (move this back one square every round. Will push cars behind it back as well)
7-8   Fast car (moves forward one square every round, changing lanes if blocked and side lane is open. Will not push cars in front of it)
8-10  Large truck (takes up 1 extra square forward)
11-20 Car

Roll for traffic pattern as neccessary, keeping up about 10 rows ahead of the character/NPC farthest ahead, then for each vehicle roll to find out what it is. Traffic is for all purposes stationary (assumed to be going at highway speed), with the exception of the fast and slow cars). All involved in the chase move at 1 square per round, 2 if they go at all out speed.

You can attempt to drive between two vehicles in adjacent lanes as long as you're driving a car or motorcycle. The drive check DC is 15, minus 5 for each SINGLE motorcycle involved (including if the character/NPC is riding one. Not applicable for 2 motorcycles driving in same lane), plus 5 for each truck involved. So for example if attempting to pass between two trucks in a car, the DC would be 25. Attempting to go between the same two trucks on a bike would be 20. Attempting to go between a motorcycle and a car on a motorcycle would be DC 5. Etc. You only need to make this check the first time you encounter a particular vehicle, so for example if you were passing between two 2-square long trucks you could go between them freely the second round.

If you fail a check, you simply stay where you are. There just isn't enough space (or you're not confident enough with the space, at least). If you roll a natural 1, you misjudge the amount of space. Make a reflex save at the same DC as the attempt. Failure indicates collision. No penalty if you successfully save.

So anyways, that's everything I've got. Any comments/suggestions would be very appreciated!

 

[RodneyThompson]

Hey, this is some great stuff! I really like it. Makes me wish I'd thought of it.

 

[JimAde]

Yep. This rocks. It begs to be automated. Do you use a laptop when you run your game?

How about a new combat action: Chuck Debris

If you drop a hazardous item out of your vehicle (like a TV, potted cactus, NPC, etc.) it "moves" backward 2 squares the first round, 5 squares the second. The driver of any vehicle whose square it passes through must make a Reflex save or hit it. DC = 20 - squares of distance when first seen.

 

[Asmor]

Glad you like it!

I don't use a laptop when we play... However when I have time I'll see if I can't whip something up in Javascript, if nothing else just as a challenge. If I do, all it'll be is just showing you the general flow of traffic. Won't take into account slow or fast cars. Will be a good way to judge the amount of distance travelled, at least.

Oh, forgot to mention, I already told the same player I'm doing this stuff for that I've got something special in store for him, and that it involves elmer's glue. Basically, when he's right behind the motorcycle they'll be chasing and boxed in between two cars, the motorcycle rider's gonna throw a water baloon filled with elmer's glue at his windshield. ^_^

I like your idea on debris. I'd like to modify it a bit to take into account things that might make it hard to dodge... For example, if you're already wedging yourself between two cars in adjacent lanes, there's not a whole lot of room to jerk the steering wheel. Maybe something like DC +10 if surrounded by vehicles in both adjacent lanes (counting any barrier along the median/side of road if applicable) and DC +20 if driving between two vehicles.

Also, I still haven't gotten around to totally grasping the driving rules... So for that would a drive check or reflex save be more appropriate?

 

[JimAde]

I also think you should disconnect the speed from the vehicle type. So you would determine the pattern (which lanes are occupied), each vehicle's type and then whether its speed is Slow, Medium or Fast. That way you can have slow huge trucks and fast motorcycles (or vice versa!). I know it's one more roll for each vehicle, but you could combine type and speed into a single percentile roll or just roll twice. As it is now, if a motorcycle is next to a large truck, they'll never separate.

 

[Asmor]

I also think you should disconnect the speed from the vehicle type. So you would determine the pattern (which lanes are occupied), each vehicle's type and then whether its speed is Slow, Medium or Fast. That way you can have slow huge trucks and fast motorcycles (or vice versa!). I know it's one more roll for each vehicle, but you could combine type and speed into a single percentile roll or just roll twice. As it is now, if a motorcycle is next to a large truck, they'll never separate.

If you want to do it like that, I'd probably base the speed on the lane then. Move the far left lane ahead one square every round and the middle lane every other round. Personally I think that's just too much book keeping for what I'm trying to achieve (I like a faster flowing cinematic/arcadey feel).

 

[Asmor]

Oh, wow, I just noticed you're from Boston! I live in Revere, and the high speed car chase in question is gonna take place on route 1. ^_^ (game's set in Boston area too)

 

[JimAde]

Oh, wow, I just noticed you're from Boston! I live in Revere, and the high speed car chase in question is gonna take place on route 1. ^_^ (game's set in Boston area too)

That rocks! I assumed it would be a freeway. You can even have intersections and cross-traffic. Cool.

Actually I'm clueless on the driving rules in d20 Modern. Having a peek at the modern SRD I find this under Combat and Vehicles:

Stunts

Stunts are maneuvers that require a Drive check to perform successfully. Unsuccessful stunts often result in the vehicle ending up someplace other than where the driver intended. When this happens, the vehicle collides with any objects in its path. Remember that the check/roll modifier from Table: Vehicle Speeds and Modifiers affects all Drive checks made by the driver and attack rolls made by all occupants of the vehicle.

Avoid Hazard: Vehicle combat rarely occurs on a perfectly flat, featureless plain. When a vehicle tries to move through a square occupied by a hazard, the driver must succeed on a Drive check to avoid the hazard and continue moving.

Object

Small (tire, light debris)5Medium-size (crate)10Large (pile of wreckage)15StructureCannot be avoided

So it appears a Drive check is more appropriate. You could just use the suggested DCs. You just have to work out the relative speeds.

Good luck with this. It sounds like fun.

 

[Asmor]

Ask and ye shall recieve!

http://asmor.homeip.net/traffic.php

You can save that as a .html and run it from any computer offline, too.

 

[BrooklynKnight]

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