Drivers . . . Chock Your Wheels

Roll-away_mixerReady Mix Trucks Rolls Away

A 48-year-old ready mix truck driver was fatally injured Wednesday April 13, 2016 while working under his vehicle, which passed over him when it started to move, then rolled about the length of a football field into an unoccupied house.

No one else was injured or hurt in the incident. The name of the driver was not released, but the driver was said to be well known and respected in his community.

Drivers . . . Chock Your Wheels

Did you know that all wheel chocks are not created equal?

The size and type of wheel chock used is really dependent on several factors including the vehicle’s size and weight and the angle of the road surface (slope or grade). There is actually a formula to determine maximum slope angle of a chock.

We’ll skip the math today, but keep in mind that parking on an angle greater than 10 degrees increases the risk of the vehicle rolling over the chock. The surface under the chock needs to be firm, as well, or the chock can be squashed down.

Parking on inclines greater than 30% gradient (16.6 degrees) is not recommended with wheel chocks. (Another sort of anchor may be appropriate for safety purposes.)

Wheel chocks are covered under SAE J348, but the standard itself is not helpful as it is under revision.

What To Know About Wheel Chocks

Wheel chocks are designed to supplement the parking brake. I can recall, for example, a time when trailers were not equipped with parking brakes and wheel chocks were essential to even unhook the trailer. Everybody carried 4x4s in the cab for this purpose. Today that is not the case, but there is still a place for wheel chocks, as large vehicles roll away every day, especially if parked on a grade, even a slight grade.

Trucks and trailers can roll-away, even if the parking brakes are set if:

  • brakes are out of adjustment
  • brakes are worn
  • brakes have been poorly maintained
  • a combination of the above

Brakes can easily get out of adjustment if a driver does not do his/her daily air-brake checks. Brakes that are out of adjustment are frequently cited on roadside inspections.

Automatic slack adjusters are really a misnomer, because if a driver does not fully apply the service brakes, the adjusting ratchet may not properly adjust. Most braking is light pressure (between 8 p.s.i. to 15 p.s.i on the application gauge). Rarely does a driver need to jam on the brakes during normal driving. But unless full-brake applications are made, the slack adjusters will not adjust themselves.

One way to help the automatic slack adjusters to properly adjust is to do daily pre-trip inspection brake checks: (a.) check the air brake gauges, (b.) do the Parking Brake Check or “Stall” Test, and (c.) the Air Loss or Leak-Down Test. They check (d.) the Low-air warning devices and do the (e.) Protection valves POP-OFF test.

Chock Your Wheels

So always use wheel chocks whenever:

  • parked on a grade
  • working around the truck
  • working under the truck
  • parked in high wind conditions
  • at docks (per OSHA or state rules)

Make sure the vehicle is always properly secure with wheel chocks . . . and it will be.

Thank you for reading this.

More  . . . Test Your Air Brakes

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