Deliberately reducing visibility at road junctions

Countess Roundabout, A303, Amesbury, Wiltshire, England (Image from Google Earth)

An increasing trend among road planners in the UK is the use of fencing, hedges or banks deliberately to reduce visibility at certain junctions, especially roundabouts (traffic circles), presumably with the intention of forcing drivers approaching a roundabout to slow almost to a standstill every time, even if the roundabout is empty. This SABRE thread has some interesting examples and discussion of individual cases (including the Countess Roundabout on the A303 – above image from Google Earth*).

I can understand the safety reasoning – and this genuinely is an architecture of control with intended social benefit – but in many places where it’s applied, I believe it to be flawed. One of the main features of roundabouts as originally introduced was that they allowed non-discriminatory free flow to any traffic which was unopposed, i.e. if nothing’s coming from the right (UK) you can proceed without actually having to halt: all roads meeting at a roundabout have to give way to whoever’s already on the roundabout. It’s the ultimate in both deference and empowerment.

By removing drivers’ ability to respond by assessing what’s happening up ahead, you reduce the amount of information available, which apart from sheer frustration, must in many cases have deleterious safety implications.

For example, I drive a low car with a relatively long bonnet. If there’s anything in a lane to my right when waiting at a roundabout, I already either have to wait until that has gone, or nose out gradually, just in order to see what’s coming and whether or not I can proceed. It’s awkward and I don’t like it. Adding high fences to the central reservation forces that situation on every driver.

As ‘PeterA5145’ notes in the SABRE discussion:

“…improving sightlines generally tends to reduce collisions at junctions. You wouldn’t deliberately engineer a road with lots of blind turnings just to make people take more care, would you?

It is nonsense to assert that slower automatically means safer.”

*This image is probably from before the fencing was put up – if anyone has a more recent one showing the fences, please let me know!


  1. marble

    I notice this at roundabouts here in Austin, Texas, that were added to my neighborhood in recent years. They are planted with various lovely bushed that impede viewing of oncoming traffic, and rather annoyed me. Your post makes me understand the rationale.

    I did notice that at least one of these has had its plants razed to a height of about one foot. Whether the city did this (perhaps under the influence of the local neighborhood association?) or an annoyed vigilante with a lawnmower is anyone’s guess. I’m just glad they did it, and I hope to see more of the same.

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  7. Can anyone help.?

    Near where I live there is dangerous country T -junction (already caused a serious accident)

    One of the problems is that the landowner has put up a greene fence which causes im paired visibilty.
    The county council have tried to take it down but say the landowner is insisting it stays.
    Surely safety must rule in these situations.
    THis fence has to be in violation of some kind of planning ?
    THis is an urgent appeal for any advice.

  8. Craig Brown

    The reduction of visibility might be very valuable at some dangerous junctions, but needs to be assessed on a case by case basis, where a need exists. It is nonsense to put it in everywhere.

    I know of one case, which was New Zealand’s worst accident hotspot until the introduction of shade cloth eliminated all fatal accidents. Follow-up research found that most drivers didn’t even notice that it was there (even those who had previously used the junction). Those that did notice did not find it to be unacceptable.

    One might indeed design a road to have less visibility (including blind turns as mentioned) or narrower carriageway, etc. depending on one’s objectives. Again, this could be done well or badly and is location specific.

    The thing to remember is that some roads should be designed for rapid motor vehicle transit and others for less rapid multi-mode use (pedestrians, cyclists, etc.). And the road environment itself should communicate its purpose and form of use (not signs). I would say that reduced visibility is often accepted whereas speed bumps, speed cameras, unnaturally low speed limits (where the road seems to afford safe travel at a faster speed) and so on can cause significant stress and resentment. One feels pretty unhappy driving at 30mph on the motorway, but it can feel enjoyable to do 20mph in a narrow rural lane with hedgerows.

    Follow-up search: self-explaining roads.

  9. Craig Brown

    This discussion has a long history. This is cut and pasted from a Smithsonian Magazine article:

    Soon after the first gasoline-powered horseless carriages appeared on English roadways, the secretary of the national Motor Union of Great Britain and Ireland suggested that all those who owned property along the kingdom’s roadways trim their hedges to make it easier for drivers to see. In response, a retired army colonel named Willoughby Verner fired off a letter to the editor of the Times of London, which printed it on July 13, 1908. “Before any of your readers may be induced to cut their hedges as suggested by the secretary of the Motor Union they may like to know my experience of having done so,” Verner wrote. “Four years ago I cut down the hedges and shrubs to a height of 4ft for 30 yards back from the dangerous crossing in this hamlet. The results were twofold: the following summer my garden was smothered with dust caused by fast-driven cars, and the average pace of the passing cars was considerably increased. This was bad enough, but when the culprits secured by the police pleaded that ‘it was perfectly safe to go fast’ because ‘they could see well at the corner,’ I realised that I had made a mistake.” He added that he had since let his hedges and shrubs grow back.

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