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Here is an intersection which always gives me trouble:

Image of an intersection

  • The usual continental European traffic rules apply;
  • There are two lanes which have right-of-way, one going towards the North-West, and one towards the South-East ;
  • There is a side-road coming in from the East (is a highway off-ramp, actually) and a side-road going to the West (a highway on-ramp)
  • In the picture, the light blue area cannot be used as it is a bus lane, but that is not important here.

If you have a car A driving along the red path, it may encounter heavy traffic on both NW and SE lanes. There is a little "stepstone island" in between the lanes so that you can proceed across the NW lane if it is free, then wait for the SE lane to clear.

While car A is waiting on the "stepstone", a car B initially on the NW lane may wish to turn to its left in order to proceed West, then also wait for the SE lane to clear.

Once the SE lane is clear, you have to decide which of A and B goes first. I am of the impression that it should be B as B is coming off the lan which has right-of-way but apparently opinions on this diverge, leading to hesitancy.

Is there an applicable rule to decide who goes first without having to resort to casting dice?

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    2 points. 1) Road rules are not homogenous over all of Europe (EG see Priority to the right) so a location tag may be useful. 2) If the point where car A enters the road is moved away from car B, then at some point A is considered as purely traveling on the SE lanes, making the default state B gives way to A – Peter M Mar 31 at 20:11
  • @PeterM Location tag added. Also, that's an interesting take, but does it really apply? – David Tonhofer Mar 31 at 20:18
  • As I have no direct experience it was simply a thought experiment, however IMHO it results in the correct answer for some given value of separation between A and B. – Peter M Mar 31 at 20:22
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Both cars have a give-way line to respect, but the one for car A is to give way to traffic approaching from its right, on the SE road which it is joining.

When there is a gap in the SE traffic, car A will get the benefit before car B anyway, so it will already be on the SE highway approaching B, when B has an opportunity to move.

Moreover, car B is crossing a major highway, and so has no priority at all.

So car A has priority over car B.


Additionally, the visibility for car B is better than for car A, because all the action is in car B's field of view. Car A, however, will be mainly focused on the traffic coming from its right, and has more difficult vision, needing to take note of car B in the opposite direction.

So for 'defensive' driving and road safety, car B should realise this, and give way.


The idea of 'casting dice' to decide is appalling. We don't make random decisions at the wheel, they must be based on taking a path that will guarantee to meet a clear road.

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  • Good answer but "they must be based on taking a path that will guarantee to meet a clear road" is to the least optimistic. One already deadlocks on the lowly discrete problem of 4 cars meeting at an intersection. And that's before we even consider the continuous and high-dimensional phase space problem of people trying to navigate roundabouts. Probabilistic/randomized algorithms are robust solutions for the real world. – David Tonhofer Mar 31 at 22:06
  • Thank you, what I meant was that you must be certain at all times that the piece of road you are about to occupy will be clear. No guesses, no optimism, but it might involve an assessment of what changes other drivers will make to their progress. – Weather Vane Mar 31 at 22:16
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    @David We don't have 4-way stops in the UK (nor I believe in continental Europe) and Europeans manage fine with roundabouts (more practice). A UK mini-roundabout can briefly deadlock but I've never seen this last for very long. (By briefly I mean 10s of seconds.) – Graham Nye Apr 1 at 0:18
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    In UK deadlocks are usually resolved by eye contact, gestures and invitation, the vehicles being quite close to each other, and on roundabouts the rule is clear: give way to those already on the roundabout. – Weather Vane Apr 1 at 7:29
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    @WeatherVane - in New Jersey (USA), at least in the 1980's, traffic entering the roundabout had the right of way. Don't ask me why... – Jon Custer Apr 1 at 13:21

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