Got vehicles working - should I go SP or MP?
Wow, cheers for all the ideas guys ^^
I made a little start earlier - as a coop racing map and it's pretty fun!
So far I've got:
-outdoorness with skybox
-bloody massive level, so no tight corners
-Jumps
-pits with light bridges that the other player can trigger off by driving over a button (drop your opponent)
-Some light bridges blocking jumps
-Funnels that can suck up your opponent
-Laser grids
In the process of adding:
-Bits to shove your opponent into liquid
-Faith plates
-A burning ring of fire. (win)
-Some rockets mebbah (cheers for that one)
-Turrets with a bigass push force (cheers for that one too)
-Lasers which can be blockedunblocked to do stuff
There's an issue with portals and world portals though :
It seems vehicles (well driveable ones anyway) cannot make it through portals. Even world portals.
I'm not sure if it's to do with it being the driveable entity or the game having hardcoded rules for certain vehicle scripts (i.e. if you rename jeep_test.txt to airboat.txt and use that, it'll behave *wildly* differently, so some parts are clearly hardcoded!). Still, portal has plenty of cool stuff to play with!
This'll be my first antiquated map, so it'll be quite shit or quite nice... but either way it'll take a while 
Aw, no portals or world portals?
Anyway, I have another idea..
a func_tank to aim at each player, and that shoots an env_portal_laser that isn't lethal, and is a bit slower than the player can drive, so if you slow down for some reason you start getting zapped. idk if you can adjust the speed at which it aims, I've never used them before. Its kinda a "i dont no what a func_tank does but i herd about it alot" situation.
And what about triggers to randomly drop a storm of cubes somewhere on the map (maybe a bit behind the trigger so the person who drives through it isn't hit with cubes, but the person behind them is), so you can ram in to them and be slowed down. Maybe a trigger_once, tons of those cubes with draw and motion disabled up above, and ontrigger <cube name (every cube has the same name in each group)> enablemotion and ontrigger <cube name> enabledraw?
You could make a small race beforehand to see who gets to put bomb on the other player's car. That would be interesting.
My steam profile: http://steamcommunity.com/id/tanger2b/
My speedrun and blind run filled youtube: http://www.youtube.com/user/portal2tenacious
I need maps to play and rate! Post links here: http://steamcommunity.com/groups/Portal2STUD
Tanger's post gives me another idea (I'm just full of ideas for this), what about (if you know how to get it to work, which judging by one of your maps you might) a stick gel bomb cannon, so you can drive on walls (as a shortcut). obviously activated by a trigger, maybe one that resets every lap.
@Alexander Bell
I have been considering adding weapons to the cars, but honestly I'm getting a little sick of the func_tanks. I used them in Funk Tank,Cube Dozer and PortalCraft and honestly they're so much trouble : They have a natural sort of lag, dragging behind the player slightly, and have issues pointing too far down or too far up. On top of that, env_portal_lasers tend to snap towards horizontal within a few degrees which messes up aiming (when they're stuck to func_tanks), and to activate the tank the player has to hit use on the tank itsself. (i.e. you have to force a +use -use).
I'm thinking if anything, I'll just make the car fire rockets in the direction the car faces!
Driving on certain walls could be fun! I did a similar thing in gMod and it worked fairly well but again, there are limitations like in Prey, and the map has to be built with a certain block type. (ALthough at least with a car, the entire level wouldn't have to be rotated!)
So many nice ideas that are such an ass to implement >.<
Dropping loads of cubes on the car though? I like that one. Perhaps they could be primed to explode on impact. Actually, I love that idea! Like a little minefield
@tanger
Heh, maybe not a pre-race.. but the player could hit a trigger that spawns a bomb on the player's car. That'd be pretty fun!
Do funnels also carry away vehicles? Because that could be hilarious.
Yes they do, and it is 
Is there a way to make vehicles degrade? they could get slower as they go, and then you could have to get a "tuneup" in a pitstop lane, and you could be held in a funnel while robo arms play animations with sparks and stuff...
Haha, gonna stop you there man - I'm fairly lazy and that sounds like a lot of tedious work >.<
Vid looks nice.
I have one more suggestion that should be pretty easy, which would be for an outdoor map... maybe a crosswalk thing with exploding frankenturrets walking across it in both directions.