Maximum Road Grade for 20-Tonne Load Capacity Trucks: Insights and Safety Tips
When considering the maximum road grade that a heavy truck can handle, particularly for 20-tonne load capacity trucks, several factors come into play, including engineering, driving techniques, and practical experience. In this article, we explore the limits and offer valuable insights to ensure safe and efficient road travel.
Understanding the Limits of Road Grades
While there is no definitive limit to the road grade that a 20-tonne truck can handle, practical experience and rules of thumb provide some guidance. In the U.S. and Canada, a common guideline suggests that no road grade should exceed 6%. However, certain areas may have higher grades, such as 7%, but these are rare and not typically found on major highways.
Practical Experience with Large Tractors
The author's personal experience with large tractors, which have a significantly higher load capacity, offers insight. These massive rigs can navigate very steep grades with ease, suggesting that a 20-tonne truck would have no trouble at all on these conditions. The key to navigating a steep grade is adequate power and proper gearing.
Ascending Grades
When ascending a grade, if your truck has sufficient power and proper gearing, you can climb even the steepest hills safely. For instance, the author has driven up very steep grades using second or even first gear, starting at the bottom to ensure safety. While it may take several minutes to climb the hill, this exemplifies the nature of the roadwork that these trucks perform.
Descending Grades: Critical Safety Considerations
One of the most critical aspects of driving on a grade is safely descending. While heavy rigs are equipped with engine brakes, not all trucks have this feature. For those without engine brakes, it is essential to be cautious and maintain proper speed.
According to the author, if a big rig is smoking or on fire halfway up a runaway truck ramp or at the bottom of a cliff, it typically indicates that the driver was going too fast and was not using proper driving techniques. To safely descend a steep grade, always use the proper gear, ensuring that you are in control of the vehicle. For large grades, the author suggests staying in second or third gear and setting the Jakes engine brakes to maximum.
Example of a Challenging Grade
A particularly challenging stretch of road is Cabbage Hill on I-84 in Oregon, which is about seven miles long and varies from 4% to 6%. The author has managed to take 150-ton loads down this grade without touching the brakes once. By coming off the top of the hill in second or third gear, setting the two-speed rear ends to low if the rig has them, and maintaining around 3 to 5 MPH, even with mid-to-high RPMs, the descent can be controlled effectively using the Jakes engine brakes.
Practical Limitations and Additional Considerations
While personal experience suggests that a 20-tonne truck can navigate increased road grades, the practical limit is likely around 14 to 16%. Military trucks or specialized vehicles might be able to handle steeper grades, but the average commercial truck is not designed for such inclines. Additionally, if your fuel tank is not full enough, the pickups might start to suck air, adding another layer of complexity to descending grades.
Conclusion
In conclusion, while there are no strict limits to the road grade that a 20-tonne truck can handle, practical experience and safety considerations suggest that 14 to 16% might be the absolute limit. Maintaining proper technique, adequate power, and using available safety features such as engine brakes are crucial to ensuring safe and efficient travel on steep grades.
Related Keywords
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