This accident happened this morning on I-5 (Interstate 5) south of Salem, Oregon. Notice the HazMat placard with the number 1760. This is a corrosive liquid described in the Oregon State Police report of the incident as alkaline copper complex. The weight of the load was 4,500 pounds, a relatively light load. Fortunately the tank did not spring a leak.

This type of separation can happen about 4 ways. The pin on the trailer that hooks to the tractor's fifth wheel could break off (almost impossible). The truck driver could have improperly hooked his tractor to the trailer. If this happened, the trailer would never made it this far. The fifth wheel, the unit on the truck that hooks to the trailer, could have been faulty or a part on the fifth wheel failed. The last possibility is that the fifth wheel was not properly adjusted. Once again, the truck would never have made it this far.

The Oregon State Police suspects equipment failure as the cause of the separation.

One more thing. When a trailer separates from a tractor like this, the air brake lines either disconnect or break away. This causes the air brakes to set automatically. You can see the skid marks behind the trailer. This is a great safely feature of air brakes.