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Why are roundabouts not made flat?

  • 25-09-2015 7:41am
    Registered Users Posts: 262 ✭✭guylikeme

    Alot of Motorway (for example) exit/slip roundabouts seem to have a very steep gradient (examples M6 exits 8 and Tyrellspass, Kinnegad..countless others).

    Sightlines for this are fairly poor considering the quality of road one is entering or exiting. You don't see the traffic on roundabout until very near the yield sign in some cases. Standards out the window IMO. Is it this bad abroad?


  • Registered Users Posts: 3,100 ✭✭✭hi5

    If it was flat then it would be on the same level as the motorway, so how would you get across the motorway:confused:

  • Moderators, Sports Moderators Posts: 14,600 Mod ✭✭✭✭CIARAN_BOYLE

    Are you saying that you want less roundabouts like this where you cant see the otherside of the roundabout


    and more like

  • Closed Accounts Posts: 4,042 ✭✭✭ Callan Harsh Umpire

    Cause people would just drive straight over them. You underestimate the stupidity and ignorance of the average motorist.

  • Registered Users Posts: 164 ✭✭Deminiman

    Some planners consider it a safer option if motorists cant see all the way round. They believe motorists will travel slower in these instances. Who really knows...

  • Banned (with Prison Access) Posts: 1,311 ✭✭✭Chemical Byrne

    Exactly, if motorists can see all the way around they will be less likely to negotiate them at a safe, low speed. By blocking the view of the far side by embankment, vegetation etc, it forces drivers to slow down on approach.

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  • Closed Accounts Posts: 1,488 ✭✭✭mahoganygas

    The gradient from the center to the outside has to be downhill. This is an intended design feature.

    As the driver turns right around the roundabout the car will bank downhill away from the roundabout. It slows the driver down and brings the car away from other cars on the roundabout if something goes wrong.

    Originally roundabouts were designed giving those approaching with right of way to those already on the roundabout. It meant that cars approached at high speed knowing they had right of way. This system didn't work so they changed it allowing those on the roundabout having right of way, and the steeped gradient away from center to slow cars down further.

    American drivers did not trust roundabouts on the old system as they caused a lot of accidents. When the UK brought in the new system, the US were hesitant to adopt the safer model. This is part of the reason why there are so few roundabouts in the US.

  • Registered Users Posts: 6,362 ✭✭✭Pete_Cavan

    It is probably a design feature to create a demarcation between differing standards of roads. After cruising along a motorway, it is no harm to make drivers stop as an introduction to the regional/local road they are coming onto. The roundabout shouldnt look like a freeflow junction. You might say that is stupid but we too regularly have people drive the wrong way onto slips to motorways, that is the kind of person roads have to be designed for.

  • Registered Users Posts: 7,731 ✭✭✭munchkin_utd

    I dont quite see the problem.
    The yield sign means you have to slow down and prepare to yield to oncoming traffic.

    If you cant see uncoming traffic till you are nearly at the yield sign, then what about it.
    Should a junction be designed to allow you to come onto a roundabout at 50 or 80 kmh or what? And how do you propose to brake if someone comes round the roundabout and is there just as you are timing your speedy entry onto the roundabout.

    And to taper onto the last post. It indeed is no harm to slow down the motorist a bit to get them to subliminaly cop on to the fact they are off a motorway. The exits on the ballincollig bypass can be taken at 120kmh....... but is that a good thing when you essentially have to stop at the top for oncoming traffic, and even there with shallow slip roads, cars do come from sideroads or across the bridge at the last moment onto the roundabout causing you to have to stop.

  • Banned (with Prison Access) Posts: 1,311 ✭✭✭Chemical Byrne

    Roads should be designed to account for the fact that most people are sh!te drivers.

  • Registered Users Posts: 2,126 ✭✭✭KwackerJack

    Irish drivers have no idea how to use a roundabout and you want to make them flat?

    Have you ever seen the chaos in towns where they have flat roundabouts!!

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