Negotiating Downgrades

Objective: To prevent loss of control accidents on downgrades by proper brake system maintenance and by developing the skills and knowledge needed to safely negotiate a downgrade.

Description: The main reason for loss of control on downgrades is brake failure, and the main reason for this is the use of improper control techniques by the driver. The brake system may be damaged or maladjusted and may not have sufficient capacity for downgrade control. Primary countermeasures for preventing a runaway are: adequate driver skills; frequent checks on brake operation; adequate preventive maintenance.

Questions for Management:
  1. Have drivers been trained to properly control their vehicles on downgrades? How? When? By whom?
  2. Do drivers know how to select proper gearing for downgrade descents?
  3. Do drivers know how to check the condition of braking systems?
  4. How often does the maintenance crew inspect and adjust brake systems? Is this frequent enough?
  5. If vehicles are equipped with brake application pressure gauges, do drivers know how to use them?
Maintenance Checks:
  • Frequent brake inspection and adjustment. Inspect and adjust brakes more frequently for vehicles used in mountainous terrain. For cross-country trips, check after every trip.
  • Do not wait for slack adjustor stroke to exceed maximum permissible. Adjust to minimum acceptable stroke whenever convenient.
  • Make every effort to replace aged brake lines and diaphragms before they fail.
Driving Tips:
  • The gear to select for descending a grade should be no higher than that required for ascending the same grade. Some vehicles may require lower gears going down than going up. Know your vehicle.
  • Doesn’t use more than light (10 psi) brake pressure to retard speed. If speed cannot be controlled with light pressure, use a lower gear ratio.
  • Do not use hand lever to apply only trailer brakes. You could overheat trailer brakes and not have enough capacity in tractor to control speed adequately.
  • Stop, put truck in proper gear and check brake function before descending long, steep grades.
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