Underground Enclosures – What do the load ratings mean?

I have been selling underground enclosures for over 20 years and one question always seems to always come up and the answers vary: What tier rating do your enclosures need to be?  So many times, the response I get is ‘Traffic Rated’.  Okay, what do you mean by ‘Traffic Rated’?  Is it being installed in the road and will have constant traffic or will the traffic be non-deliberate?  Most of the time we will go back and forth trying to determine what the customer’s real needs are.  Hopefully this information will clear this dilemma up.  Here are what the various tier ratings mean.

Light Duty – Pedestrian Traffic Only    

These units usually have a design load of 300 pounds per foot and have been tested to around 3,000 and should only be installed in a pedestrian traffic only area or greenbelt.

Medium Duty – Tier 5 – Tier 8 – Tier 15

All of these tier ratings fall under Medium Duty but vary where they can be installed.

Tier 5  

Sidewalk applications with safety factory for non-deliberate vehicular traffic

Design Load:     5,000 lbs

Test Load:         7,500 lbs

Tier 8

Sidewalk applications with a safety factory for non-deliberate vehicular traffic

Design Load:     8,000 lbs

Test Load          12,000 lbs

Tier 15

Driveway, parking lot, and off-roadway applications subject to occasional non-deliberate heavy vehicular traffic.

Design Load:     15,000 lbs

Test Load:         22,500 lbs

Heavy Duty – Tier 22

We are still talking about non-deliberate traffic.

Tier 22

Driveway, parking lot, and off-roadway applications subject to occasional non-deliberate heavy vehicular traffic

Design Load:     22,500 lbs

Test Load:         33,750 lbs

AASHT0 H-20

Here is the true ‘Traffic Rated’ product for continuous roadway traffic

The following conditions should be considered for a Traffic Rated enclosure:

Vehicle class up to Class 8

Gross vehicle weight up to 40,000 pounds

Maximum wheel load of 16,000 pounds

Design Load:     16,000 lbs

Test Load:         34,720 lbs

Continuous roadway traffic

As you see there are many different options so it is very important to know the application so that the correct product is selected.

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