24 December 2012

Roadside trees can affect traffic speed

Motorists who travel down French-style avenues feel as though they are going faster and are more likely to slow down. 
More than 200 trees were planted on the approach roads to four rural villages in north Norfolk which had a history of speeding problems...

Provisional results found that drivers reduced their speed on the roads into Martham, Horstead, Mundesley and Overstrand by an average of two miles per hour...

By strategically planting trees along the roadside the driver's perception of speed can be altered. As the car approaches the village the trees are planted closer and closer together giving the impression that the vehicle is moving faster. This encourages the motorist to slow down.  
More details at the 2010 Telegraph article.   I have no doubt about the physiology and psychology of the effect, but another consideration I've noticed when driving down avenues of trees is that, depending on time of day and orientation, the trees can generate a stobe-like effect as they block the sun from the driver's eyes.

Image credit:  Warren Photographic.


  1. We did a similar thing on some streets in the small Florida Village where I live, for the same reason, along a couple of long straight 30 mph roads. What we discovered was that you didn't need to plant the trees at regular intervals, or even always right next to the road. We staggered the distance between trees and from the road edge, for a more natural effect. Works just the same.

  2. I live in semi rural new england and the trees don't seem to slow down morons the slightest bit....well except for when the car meets the trees.

    1. I have to agree. In the area where I live, trees don't seem to slow the morons down..... If anything, it appears to cause them to SPEED UP.

  3. I would argue that it's not the perception of going faster that slows people down. Rather it is the fact that the trees are RIGHT BESIDE THE ROAD. Drivers know that the slightest mistake can end in death or injury...so they slow down.

  4. The added danger hardly seems productive...

  5. I almost fell off the back of a motorcycle once on a late afternoon in winter, when there was a strong strobe effect of the sun behind the trees. I was looking at the trees as we passed and began to pass out. I'm apparently subject to "flicker fits," but I had no idea this was the case until this occurred.

  6. I read an article years ago that the French were cutting those trees down precisely because of the Darwinian impact on careless drivers.

  7. The strobe effect can cause epileptic fits. Long ago I heard that the French author Albert Camus crashed and died because of that.

    I don't think this is a good idea at all. Better to simply lower the speed limit and/or put in rumble strips. If you ever go to Mexico, they have the worst system ever for drivers, but it saves lives. They put "topes" - good old fashioned speed bumps - at the entry to almost every small town. And you never know what KIND of speed bump it is. Some are darned near impossible to go over without slowing almost to a stop. I have NO idea how much it costs their economy, but people don't get hit by cars. And isn't that the real reason for slowing people down?

    But 2 mph? Piffle! If that is all it slows people down by, it is worthless.

    Real story: My home town had trees close to the pavement like this on one street, on a curve. A kid was driving the 30 mph speed limit (witnesses swore he wasn't speeding), and he drifted a little bit too much. 30 mph killed him. So, yes, the trees that are that close to the pavement are DANGEROUS. And 2 mph on a country road? What does that do? Bring the speeds down to 53 mph? 43? If someone hits them and dies, the family could get a good lawyer and bankrupt the town.

    A really, REALLY bad idea.


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