2 lanes going straight on.

**Timbuk2**

This is something I've seen quite often, mostly around Dublin (moreso than anywhere else).

At a crossroad, there are two lanes - and the left lane is labelled 'Straight on or Left' and the right lane is labelled 'Straight on or Right', except there is definitely only one lane on the straight-on road.

Example 1 - Belgrave Square, D6 (trust me, underneath the van, there is a straight on or right symbol).

Example 2 (Pearse Street / Macken Street)

Example 3 (Fr. Griffin Road, Galway)

And they're just the ones I can remember driving on, I'm sure there are plenty more. I seem to remember there being something like that on the Dundrum Bypass but I can't find it on Google Maps.
Is there a purpose to this? Some of the roads are not even heavily congested, so I doubt it's to stop building up queues. It forces traffic to merge on the junction which seems wholly illogical. Most of the time, there is a logical lane to use (for example, use the left lane to go straight on, otherwise you'll be waiting behind traffic looking for a gap to turn right), but sometimes it's not all that obvious. This is not helped by the fact that traffic stopped at the junction can often block road markings, meaning that somebody may not be aware that they should merge on the junction before arriving at the other side.

Do you mean here on the bypass?
dundrum bypass
we had an argument about that one on Motors a while back and I think the consensus was that nobody had a clue why they designed it that way. I usually end up turning left on that road anyway (long way around to the shopping centre:pac: ), but if you do want to go straight on in practice, you'd want to be in the right lane or you'll be in trouble, due to the merging later on and all the locals deciding that's the correct lane
edit: there is a filter left light there as well though - so I suppose it makes more sense to stay right, I'd forgotten about the light



harold's cross road going straight on over the bridge is another one but everyone there goes into the left lane for straight on
In those cases you'd just have to know how the traffic goes and know the area or you're in trouble I think

seamus

There is sometimes an indicator on the far side of the road in terms of who is doing the merging.

If you look at the image of Harold's cross that bluewolf posts above, for traffic coming from the city (i.e. towards the camera), you can see a "keep right" or "move right" arrow before the bus lane. This indicates that the traffic in the left-hand lane must move right, effectively requiring them to give way to traffic in the right-hand lane.

In the absence of lane markings, this isn't actually a rule, rather something to keep in mind. Sometimes you'll see this marking on the left, sometimes you'll see it on the right. Take this marking as a rough rule of thumb in terms of which lane is doing the merging. Most of the time though there is no such marking, so I tend to go with giving right of way to whoever is "in front" of me.

The purpose of the "straight or right", "straight or left" marking as I understand it, is to allow traffic to choose the best lane taking into account the traffic conditions. Basically if you want to go straight ahead, you can choose either lane and avoid being blocked by right or left-turning traffic. If the left-hand lane was left-turn only, then straight-on traffic would have to wait for right-turning traffic before they could proceed through the junction.

The only logic I can think for the Galway one Timbuk2 has posted is to allow people to use the right-hand lane to go straight on if the left-hand lane is blocked by people going in and out of the shops on the left.

This kind of merging isn't limited to straight-on lane either. At the Tallaght bypass (N81) eastbound, turning onto the Old Bawn road, there are two lanes which merge into one as soon as you've turned. It works though because the Old Bawn Road has pretty good capacity at that point, so it doesn't act as a bottleneck. Don't recall any problems or near misses on it, everyone seems to understand what to do.

robbie1876

My rule of thumb at an unknown junction where this is the case is to look at the traffic lights and see if there is a chance of a filter arrow in one of the lanes. Eg in bluewolf's dundrum link, it looks to me like traffic in the left lane could be given a green arrow to turn left before the traffic going straight gets the all clear, so in this case I'd stay right. In the Harolds Cross example I think I can see a right filter, so I'd keep left.

Thus reducing my chances of being beeped out of it...

Jimmy Bottlehead

There's one of those in Phibsboro too, both lanes just merge like a zip. Doesn't make a whole lot of sense though, but it also highlights the fact that we should have overhanging signs as well as road markings.
Bloody impossible to know which lane is which in an unfamiliar area with traffic covering the markings.

**Timbuk2**

Thank you for the helpful answers, bluewolf, Seamus, Robbie and Jimmy Bottlehead!

That's a very good point about filter lights, definitely something I hadn't considered!

And yes, bluewolf, that is exactly where I was talking about on the Dundrum Bypass - didn't realise it had been discussed in Motors!

Thanks again!