Trees have been known to have hundreds of benefits. But who would guess that they can make streets safer. And despite the fact many traffic engineers have felt that trees are dangerous for motorists as they narrow lanes and  obstruction things like parked cars, other engineers have proven this theory wrong. How?

Studies have been made on the correlation between streets and accidents and streets that are wide open and streets that are tree lined. It has been shown that streets that are wide-open seem to encourage motorists to speed and therefore with speeding comes more accidents. On the flip side, streets that are tree-lined encourage motorists to slow down and drive more cautiously – which of course means fewer accidents.

It seems, trees provide visual cues to drivers about their speed and send signals back to them for potential of collisions, which in turn makes the driver slow down. Trees also create physical barriers between motorists and pedestrians and trees seem to make drivers calmer.  As for their other benefits, trees give shade on hot days, absorb exhaust, produce oxygen and can even extend the life of pavement by 40 to 60 percent.

Eric Dumbaugh, an assistant professor of transportation at Texas A&M is the man who decided to prove his theory of how trees created safety rather than detriment on streets. He published his findings in the Summer 2005 issue of the Journal of the American Planning Association. Among the cases cited in his JAPA article are these:

* A study of five arterial roadways in downtown Toronto found that mid-block car crashes declined between 5 and 20 percent in areas where there were elements such as trees or concrete planters along the road.

* Urban village areas in New Hampshire containing on-street parking and pedestrian-friendly roadside treatments were two times less likely to experience a crash than the purportedly safer roadways preferred by most transportation engineers.

* A study of two-lane roadways found that although wide shoulders were associated with reductions in single-vehicle, fixed-object crashes, they were also associated with a statistically significant increase in total crashes. A rise in multiple-vehicle crashes offset the decline in fixed-object crashes.

* An examination of Colonial Drive (State Route 50), which connects the north end of downtown Orlando to the suburbs, found fewer serious mid-block crashes on the livable section than on a comparison conventional roadway. According to Dumbaugh, the conventional roadway also was associated with more injuries to pedestrians and bicyclists.

Dumbaugh followed up his experiment with an article on findings he examined safety on three routes- State Routes 15 and 44 in DeLand, Florida, and State Route 40 in Ocala, Florida. Each of these routes have pedestrian-friendly designs along parts of their length and conventional designs along other sections. Dumbaugh discovered that the pedestrian-friendly segments experience 40 percent fewer crashes than comparison roadways.

Having this information has helped city governments integrate more trees into their landscapes, an idea they have liked all along, not only for safety reasons but also because for planners, streets are more than throughways for traffic. They are also public places where people walk, shop, meet and engage in various social and recreational activities. This in turn creates pedestrian friendly streets that are highly desired by homebuyers, thus driving the value of homes up.

Trees have value in nature as well as in public places, aesthetically, environmentally and now for safety.

About the Author: Andrew Johnson is the owner of Central Texas Tree Care, a leading provider of Austin tree services in Central Texas. Certified ISA Austin arborist services including: tree trimming, tree removal, tree care and stump removal. For more information on Austin tree service please visit

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