Grade limits depend on trailer configuration, load weight, weather conditions, and available power.
General guidelines for heavy haul grades:
Upgrade Limits (Traction)** - Standard heavy haul: 6-8% maximum sustained - Extreme loads: 3-5% maximum sustained - Winter conditions: Reduce limits by 30-50%
Downgrade Limits (Braking)** - Standard heavy haul: 6-8% maximum sustained - Extreme loads: 4-6% maximum sustained - Longer descents require lower grade limits
Factors Affecting Limits** - Gross combination weight - Number of drive axles and power available - Trailer braking capacity - Road surface condition - Weather conditions
Safety Margins** Always apply safety margins: - Known routes with good conditions: 10-15% margin - Unknown routes or variable conditions: 25-30% margin - Extreme loads or critical moves: 50% margin or more
These are guidelines, not rules. Each load and route requires specific analysis based on actual equipment and conditions.