3.4.2 Planting Location

Mature size of plant material should be considered in determining its placement. Plant material within the ROW should not obstruct clear sight lines, unyielding structures, or create maintenance difficulties.
Figure 3-6
through
Figure 3-9
show different planting examples.
  • Clear zones:
     Plants may not be placed where they block the ‘unobstructed, traversable area beyond the edge of the highway’. Refer to the
    RDM
    for specific linear distances.
  • Unyielding structures:
     Plants must not obscure any unyielding structure within the clear zone (drainage culverts, etc.). Avoid landscape design situations that would require personnel and equipment to be on the driving lane side of guardrails and concrete barriers or on the shoulders of high-speed, main-lane traffic.
  • Signs:
     Plant material with the potential to block any portion of the sign face should not be placed in front of the sign.
  • Medians:
     Provide 3’ minimum clear setbacks along the median edge for maintenance safety. Plant material height at the median nose should be 30” height maximum. Verify exact heights with specific District.
  • Adjacent to walls:
     Concrete mow strips (minimum 12” width) should be installed immediately adjacent to the wall face. Plants should not be placed any closer to a wall structure than half the expected mature spread of the plant.
  • Elevated roadways:
     Plants should not be placed where foliage may intrude to within 10 feet of the travel lane of elevated roadways and bridges.
  • Utilities:
     Trees should not be located where the mature height or spread will interfere with utilities. Verify tree species with appropriate overhead utility agencies.
Median planting can add color and visual separation between driving lanes.
Plants are effective for visually softening tall retaining walls or noise walls.
Figure 3-7: Plants are effective for visually softening tall retaining walls or noise walls.
Vegetation with low maintenance properties is a good choice for screening.
Figure 3-8: Vegetation with low maintenance properties is a good choice for screening.
Street trees