November 12, 2019
Driving the Houston freeways is a little greener than the rest of the state.
Houston is a leader in planting trees next to highways, according to the Texas Department of Transportation, the state agency that manages highways. Green on highways improves public safety by reducing pollution and removing the monotony of driving, experts say.
TxDOT hopes to have planted 2 million trees next to highways in Houston District as part of the division’s Green Ribbon project by the end of 2020, spokeswoman Deidrea George said. The goal is to plant another million trees by 2030.
The Green Ribbon Project began in 1999 to restore natural beauty along Texas’ highways by turning concrete-dominated landscapes into green ribbons.
As TxDOT prepares to expand Interstate 45 in the coming years, tree planting remains part of the department’s plan to mitigate the impact.
One reason trees are planted along highways is to improve road safety by giving drivers a visual break.
“It can reduce driver concentration a little from this highway hypnosis,” said Bert Cregg, professor of horticulture and forestry at Michigan State University.
Cregg is working with the Michigan Department of Transportation to add bushes and grasses in addition to freeways in suburban Detroit.
Trees, wildflowers, and shrubbery are all effective in making freeways visually interesting to prevent freeway fatigue, Cregg said.
According to a study published by the Institution of Transportation Engineers, suburban drivers drove 3 miles per hour slower when there were trees.
Other benefits of planting trees near highways are that they can prevent the spread of engine exhaust and make areas that would normally be lacking greener.
Gary Johnson, a professor in the Department of Forest Resources at the University of Minnesota, said that when an area loses trees, there is an increase in people with breathing problems.
Green on the roadside offers aesthetic and safety advantages, but poses additional challenges for transport engineers.
With the green comes the animal world that seeks shelter and food. Small mammals crossing highways become more common when trees are planted next to highways.
“We tend to view wildlife as a good thing,” said Cregg. “But people might want to dodge and miss them. That could be something else that is raised as an objection. “
Nuts, fruits and branches of trees also bring dirt onto the road. Heavy rainstorms loosen the soil around trees and make it easier for them to collapse on roads.
While trees help with rainwater runoff, soil erosion caused by trees remains a bigger problem, Cregg said.