12.1 Tree planting and road visibility

FIGURE 12.1

Tree planting and road visibility

No trees or shrubs here

No trees or shrubs here

No trees or shrubs on the inside of cut slopes around curves

Source: MetaMeta (www.roadsforwater.com). No trees or shrubs on the inside curve of an embanked road construction

or exits. overgrown trees are a particular problem and care should be taken not to plant trees with horizontal crowns.

Road safety

Road safety is an extremely important factor when designing roadside plantings. Trees can contribute to fatalities in run-off-road collisions, particularly in highspeed zones (Budzynski et al. 2016). Trees are one of the major factors in deaths on rural roads in many countries (photo 12.3).

Tree planting should not compromise road safety. Tree planting should not be undertaken in high-speed zones and should be kept a safe distance from the carriageway in medium-speed road segments (see table 12.1). If a road is upgraded, trees may need to be cut down to ensure safety. a minimum 20-meter offset is required for all speed zones above 40 kilometers an hour. Regardless of the speed zone specified, the actual mean speed of travel for any new road cannot be known in advance. Run-off-road crashes have high-severity outcomes and are among the most unforgiving types of collisions.

Distance to electricity lines

Contact between trees and electrical wires and poles should be prevented. a lateral distance of 8 meters from the utility wires should be maintained to minimize interference. Very tall trees should not be planted in the vicinity of electricity lines in rural areas.