Event planners usually try to make many of the instructions tricky or ambiguous and much of the skill in these events is to identify any traps and avoid them. Four wheel drive turbo cars have taken over at the top end but have had little impact at grass roots level so far. Crews following the correct route will pass observation points where information has been planted and record these on their 'road card'. The winner of the trial is the crew which covers the course most correctly and in the shortest time. Points are lost for travelling in the wrong direction, missing 'informations' or even missing whole sections of the course.
Speed is important but accurate map work is the most critical aspect.
This is a real team event. Car preparation, map work, fast precise driving and good communication are all key factors in competitive crews. Trials are most usually conducted in large forests in the dead of night. The cars are usually older model rear wheel drive four cylinder vehicles which have been extensively modified to suit them to this type of competition. They have roll cages, special tyres, modified brakes, the addition of a very effective hand operated brake on the rear wheels, a special trip meter for the navigator called a Halda or Terratrip and a lot of body strengthening and lightening.