Zone of Intrusion and Concrete Barrier Countermeasures

The concept of zone of intrusion is not yet widely documented in the highway geometric design industry. This paper extracts criteria from crash testing literature, to account for the critical offset behind the face of barrier – to prevent vehicles snagging on vertical fixed objects. Reference tables are developed that provide zone of intrusion criteria for different design speeds, test levels (design vehicles), and barrier heights. This information is useful to allow designers to optimize countermeasures; in particular beside: columns, bridge abutments, retaining walls, guide sign poles, and luminaires. Examples are presented for: – selectively pinning or buttressing free-standing barriers to eliminate sliding distance; – applying short lengths of higher barrier adjacent to hazards; – placing free-standing barrier beside retaining walls, instead of moment slab parapets; – load distribution on structures, through the use of A-frame pole structures; and – L-shaped foundations, to integrate with adjacent cut and fill slopes or avoid utilities.