©2006 Alliance Construction Technologies
B1 • Urban and suburban areas with numerous closely spaced obstructions having the size of single-family dwellings or larger that prevail in the upwind direction from the sound barrier for a distance of at least 1500 feet.
EXPOSURE CLASSIFICATION (AASHTO)
B2 • Urban and suburban areas with more open terrain not meeting the requirements of Exposure B1.
C • Open terrain with scattered obstructions. This category includes flat, open country and grasslands. This exposure shall be used for sound barriers located on bridge structures, retaining walls, or traffic barriers.
D • Flat unobstructed coastal areas directly exposed to wind flowing over large bodies of water. This exposure shall be used for those areas representative of Exposure D extending inland from the shoreline a distance of one half mile.