Issue: November 9, 2002
Please help! Our house is just off a curved road where people have lost control of their cars and left the road. I am afraid that a car traveling too fast will cross our lawn and crash into our little boy's bedroom. Is it a better to build a hill of soil or plant a row of trees to stop cars?Answer:
It is a good idea to consider the landscape as an element to protect your family in a situation like this. A berm of soil could possibly cause a speeding car to become airborne and actually travel farther than if it stayed on the ground. A higher, steeper berm could cause injury to the driver and passengers of the car, possibly subjecting you to liability problems.
Trees may also injure people in the car, so a row of trees may also be a bad choice. It takes a long time for trees to become large enough to provide protection.
A properly designed and maintained hedge would be a better choice. You might also want to combine this with a thick layer of gravel like that found on highways in mountainous regions. Deep beds of gravel are often found on curves at the bottom of steep grades to stop run-away trucks. If properly designed, the gravel bed may remove a lot of momentum from the car without causing it to flip over. Rows of hedges just behind the gravel bed would be an attractive "safety net" to provide a little more stopping power.
The hedge should consist of plants with many small stems rather than just a few stems. The many smaller stems will yield, keeping the passengers safe, but will also serve to greatly slow the car. The hedge's height should be at least 4 feet so that the hedge doesn't lift the car into the air like the berm of soil. A hedge will grow faster than a tree, so the protection will be available much sooner. The hedge can be used to screen the view of the gravel bed from the house so that you don't see the gravel every time you look from a window. If there isn't enough room for the gravel bed, the hedge is still a good option. Several rows of hedge will serve better than a single row.
As a final protection, if you think it is necessary, a row of tall planters just outside the house may help. You can build these from concrete road culverts placed vertically and filled with soil. By the time the car reaches this point, the planters should not be harmful to the people in the car, but they will provide that one last bit of protection for your house.
A last thought would be to move the child to a bedroom in another part of the house. This may not be possible, but it would provide much greater protection for your child. What we have described here may stop a car, but a runaway truck or bus may not be so easily stopped.back to top
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Marisa Y. Thompson, PhD, is the Extension Horticulture Specialist, in the Department of Extension Plant Sciences at the New Mexico State University Los Lunas Agricultural Science Center, office: 505-865-7340, ext. 113.