Large multiple box culverts are defined as those with more than one barrel and a total opening (i.e., distance) of 20-ft or less between extreme inside faces as measured along the highway centerline. Large single pipes or single box culverts are defined as those with diameter or height exceeding 5-ft or cross-sectional area exceeding 25-ft

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From a safety standpoint alone, treatment for both new and existing installations should be considered in the following order:

Designers should carefully consider several factors before opting to use safety pipe runners. Where a defined channel is present, it may be impossible or impractical to shape the terrain near the culvert end to provide for vehicular traversability. Such circumstances would dictate that a more suitable, culvert end treatment be selected.

Meeting clear zone criteria does not eliminate the obstacle of the culvert end, rather the obstacle is placed at a location where it is less likely to be struck. Although not as desirable as providing a traversable culvert end, it is preferred over barrier treatment where there is sufficient ROW and where the cost of providing the necessary culvert length is reasonable. Where the cost of added length for new culverts or of extension of existing culverts is three or more times the cost of shielding with barrier, treatment with barrier becomes an attractive alternative.

For low-volume conditions (less than 750 current ADT), the treatment option that has the lowest initial construction cost is generally the most cost-effective design if an improved design is warranted.