TIER 5

Enclosures that are located in areas that will never experience vehicular traffic such as residential lawns near a building or in a backyard.

TIER 8

Enclosures that are located near vehicular traffic, but will not be driven over. In the drawing, TIER 8 enclosures are located in a parking lot, but are blocked by concrete tire stops. Also shown are TIER 8 enclosures that are located in places that protect the enclosure for vehicular traffic, such as behind a light pole or surrounded landscaping.   

TIER 15/22

Enclosures that are located in areas that may experience non-deliberate heavy vehicular traffic. Such areas include “right-of-ways” and medians. TIER 15 enclosures should also be used in parking lots where the enclosure is not protected from traffic, such as near a light pole. It is also possible to use TIER 15 enclosures in single lane alleys as long as they are located in the center of the alley straddle the enclosure with both tires. Tier 22 should be used when enclosures that may be exposed to very heavy non-deliberate traffic that exceed the design load of TIER 15.