12 Car Rallies are Events run on the Public Highway. They consist of crews of two, a Driver and a Navigator, The Navigator has to plot a route on a Map and instruct the Driver where to go. The  Driver has to drive steadily and follow the Navigators Instructions. 

The aim is to follow the route at an average speed of 30 mile per hour. Along the route are Controls that the Crews have to visit. 
Basically there are two Types of Control – A Time Control and a Passage Control. 
At a Time Control the aim is to book in on time, if you are late you have 1  point per minute added to your score, If you book in early then you are penalised by 2 Points per minute that you are early.
A Passage Control can be either a Board or a Manned Control where you get a signature to prove that you have Driven the correct Route.

The Hardest part of a 12 Car is the Navigation which is handed out to the Crews on the Start line. 
The Navigation can consist of anything found on an Ordnance Survey Landranger (1:50000) Map. 
This can be Grid References, Map legends or Basic Instructions, eg. Turn Left, Turn Right or Straight on. 
The secret to doing well in 12 Cars is to find a Good Navigator, and the Secret to being a good Navigator is to Practice.