The following course material is for reference only. Please go to the new course to complete your Vermont certification.

 

Riding Your Snowmobile

Stopping a Snowmobile

Stopping a snowmobile is trickier than stopping a wheeled vehicle on a street or trail. To ensure that you can stop safely in any situation, you must be able to calculate a safe speed based on stopping distances.

Safe Speed

• Maintaining a safe speed allows you to control your machine and stop in time to avoid a collision.
• The greater the speed, the greater the stopping distance.
• To determine a safe speed, you must know stopping distances and how to factor in sight distance and reaction time.

Sight Distance

• Sight distance is the distance from which you can see and identify a hazard, not necessarily the total distance you can see. You often see an object before you’re able to identify it as a hazard.
• If the stopping distance to an object is greater than the sight distance, you’re in danger of hitting the object.

Reaction Time

• Reacting to a sudden need to stop involves these steps:
  • Seeing something
  • Recognizing it’s a hazard
  • Deciding what to do
  • Braking or steering around the object

Reaction Time Distance

• Reaction time distance is the distance the snowmobile travels during the time it takes you to react.
• The distance depends on the reaction time (in seconds) and speed (in feet per second), and is calculated as: Reaction Time Distance=Reaction Time x Speed.
• Accidents occur in just a few seconds, so think of your speed in feet per second (multiply mph by 1.46667).
  • 15 mph = 22 feet per second
  • 30 mph = 44 feet per second
  • 45 mph = 66 feet per second
  • 60 mph = 88 feet per second
• At 30 mph with a reaction time of three seconds, the reaction time distance is 132 feet (3 sec. x 44 ft./sec.).
  

Reaction Time Distance = [Reaction Time] x [Speed]

Normal Reaction Time
Studies reflect that a person's reaction time is anywhere from one to three seconds. In general, however, three seconds is probably more accurate.

Stopping Distance

• Stopping distance is calculated as:
  • Stopping Distance = Reaction Time Distance + Braking Distance
• Braking distance is the distance traveled after you apply the brakes. It depends on two factors: speed and drag.
• Drag factors
  • The drag factor is a measure of the friction between the snowmobile’s track and the surface it travels over.
  • Deep, powdery snow stops snowmobiles more quickly because it creates more drag than shallower snow.
  • Glare ice has less drag than deep snow, so snowmobiles travel much farther after braking.

The graph gives example stopping distances at various speeds. Note that your stopping distance could be different due to your reaction time and track conditions.