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Negotiating Curves

Objective: To prevent rollover accidents by clear understanding of how and why rollovers occur and how to judge safe speed approaching and negotiating curves.

Description: When negotiating a curve at an excessive speed, commercial motor vehicles will roll over. Automobiles will lose traction and slide out of a curve instead of rolling over. The more top-heavy a vehicle is, the more likely it will roll over than slide out of a curve. During a tractor-trailer rollover, the trailer usually begins to roll before the tractor. By the time the driver realizes that the trailer is rolling, there is not much that can be done to prevent a complete rollover.

Questions for Management:

1. Do drivers know that the posted advisory speed on curves is for automobiles, not commercial vehicles? 
2. Do your drivers know that commercial motor vehicles generally cannot negotiate curves at as high a speed as automobiles without the possibility of rolling over? 
3. Do your drivers know what conditions make rollover more likely?

Driving Tips:

• Ensure that cargo loads are secured to prevent moving from side to side. 
• Remember that top-heavy cargo will cause commercial vehicles to roll over in curves at speeds lower than those loaded with flat compact cargo. 
• Reduce speed before entering curve. If you enter curves too fast, you may not have enough time to slow down before rolling over. 
• Maintaining speeds at curve advisory may not be slow enough to prevent rollover of commercial vehicles. 
• Since trailers usually begin to roll first, you may not know you are rolling over until it is too late. 
• Slow down before you get into the curve. 
• Stay off the shoulder in curves. Your right or left side wheels may drop or sink down into a shoulder and increase your chance of rollover. 
• Slow down substantially for unfamiliar curves.

Maintenance Checks:

• Adequate fifth wheel lubrication.

Professional Safety Consulting

Professional Safety Consulting