Coming onto any dual carriageway is tricky enough. The vast majority of your observational emerging experience is judging the speed of vehicles travelling 20 to 30 mph. With a dual carriageway they could be doing anything! So, making sure you can see as far down the road as possible is important, otherwise you could find yourself pulling out in front of someone and slowing them down. resulting in a fail.
The issue with the entrance to The Portway, here in Sea Mills, is that the give way lines are in an awful position. There is no way of being able to see all the way down the street for a speeding vehicle simply by stopping at them.
The reason for the lines being so far back is for the bus stop. The bendy buses use The Portway and need additional space and time to get into the bus stop and out of the way of traffic.
So, what you'll need to do is come to the end of the road. Stop at the line. Check for the bus, then edge forward until you're in a position to see clearly all the way down as far as possible. I once saw a Porsche travelling at what must have been 150 mph plus once. It's essential to come forward enough to observe effectively for this eventuality.
You can see on the photos, the give way lines are about a car length from actually being on the actual part of the road where vehicles travel. This is close to where you need to be to be able to see properly.
You may even be able to see where the old give way lines are. Stop just before these. failing that, where the dark and light coloured tarmac meets is another easy visual reference to use.
The image on the left is to try and highlight just how far away the give way lines are from the end of the street and therefore in a poor position to observe effectively to your right before observing.