Magnitude, Touched or other?

Alright I'm a bit stuck in the making of my game. If you want to have a look at this game so far here is the link:

http://www.roblox.com/Traffic-Racer-place?id=146148373

Ok so if you've checked out the game you'll notice whilst driving the car if you hit another car nothing happens. This is obviously the next step of my game development and I'm stuck as to how I can do this. The little white squares I have purposefully left visible around the side and front of the cars are what I call 'hitsensors'. Supposedly what happens is when they hit a car they will change a variable causing another script to activate etc... But I just do not know how to make the hitsensor.. sense!

I was told use magnitude, but as you can see that would be very difficult, impractical and time consuming and knowing me it wouldn't work. Currently they have script.Parent.Touched:connect(function) in them but since my cars teleport about and do not gain velocity apparently it is not activating the touched?

How can I do this? Thanks!

P.S The whole game is local.

HitSensor.Touched:connect(function(hit) DoStuff() end)

Make sure you put this script where the parts of the car are located.

for Index,Part in pairs(script.Parent:GetChildren()) do
	if Part:IsA("Part") then
		Part.Touched:connect(function(Hit)
				if not Hit.Parent:FindFirstChild("Humanoid") then
					Part:BreakJoints()
				end
			end
		end)
	end
end